LinearView - Product Data & Applications 1/LinearView - Product Data & Applications.iso/swcad/help.txt

Text File | 1996-07-09 | 139.3 KB | 2,978 lines

<Dummy1
Line-by-Line Explanation of the Buck Spreadsheet

<vout,0
I.    Main Output Voltage--This value is transferred from
 the Design Specification screen, but you can change it here
 if you wish.
<vinmin,0
I.    Minimum input voltage--This value is transferred from
 the Design Specification screen. You should definitely change
 the minimum input voltage as part of the design procedure,
 because SwitcherCAD calculates detailed operating conditions
 only at minimum input voltage. This was done because, for
 many topologies, minimum input voltage represents a worst-case
 current condition for most of the components. In a buck
 converter, switch dissipation is highest at low Vin, but
 diode and inductor dissipation are highest at high Vin,
 and input-capacitor dissipation is highest at Vin= 2'(Vout).
 AC losses in the IC switch and diode are highest at the
 maximum input voltage. Refer to Table 5.1.1 for worst-case
 operating conditions for each power component.
<vinnom,0
I.    Nominal input voltage--This input was originally included
 in SwitcherCAD as a condition for calculating efficiency.
 It was dropped from use when the program run time became
 too long, but remains available for future use.
<vinmax,0
I.    Maximum input voltage--Maximum input voltage is used
 only to calculate worst-case voltage conditions for the
 IC, catch diode, and input capacitor.
<ioutmin,0
I.    Minimum load current--This parameter is not used in
 the buck converter program. All buck designs supported by
 SwitcherCAD operate down to zero load current. They will
 begin to operate in discontinuous mode when load current
 drops low enough, and SwitcherCAD calculates this point
 for reference.
<ioutnom,0
I.    Nominal load current--Not used. See "Nominal input
 voltage."
<ioutmax,0
I.    Maximum load current--SwitcherCAD calculates operating
 conditions at maximum load current only, so this parameter
 can be modified to observe the effect of load changes on
 various parameters.
<DVopp,0
I.    Output-ripple voltage--Ripple voltage is specified
 by the user, and SwitcherCAD tries to create a design which
 meets this specification without using an additional output
 filter. However, If SwitcherCAD decides that the output
 capacitor would be unreasonably large, it adds an output
 filter and computes values to meet the ripple specification.
 The user should carefully examine the resulting design to
 see if human intelligence judicially applied could shift
 inductor, capacitor, and frequency values to meet the ripple
 specification more effectively or economically. Many times,
 a low ripple voltage is rather arbitrarily chosen, and a
 little hard-nosed investigation will show that the load
 will actually tolerate more ripple. If this eliminates the
 need for the additional filter, everyone wins.
<tamax,0
I.    Maximum ambient temperature--This parameter is used
 to calculate the amount of heatsinking required for the
 IC, catch diode, and filter capacitors. Remember that SwitcherCAD
 calculates the minimum amount of heatsinking required to
 keep junction temperature below maximum specification. Conservative
 design suggests some guardbanding here.
When selecting filter capacitors, SwitcherCAD assumes
 maximum ambient temperature and a 20,000 hour required lifetime.
 If SwitcherCAD cannot find a filter capacitor in its database
 to satisfy the lifetime requirement, it will default to
 a 1,000,000uF capacitor. The database contains aluminum
 electrolytic capacitors rated at 105°C. If SwitcherCAD does
 not find a suitable capacitor, then you should select an
 alternate capacitor technology (e.g., Sanyo OS-CON's), use
 paralleled units, or lower the lifetime requirement and
 use the equation in Appendix A to determine the proper filter
 capacitor.
<VswM,0
I.    Maximum rated switch voltage--SwitcherCAD enters a
 value from the database for the IC it has selected. This
 can be altered for special purposes, but if it is increased
 the resulting design may violate LTC's data-sheet specifications.
 It is the user's responsibility to ensure that the IC is
 not subjected to over-voltage conditions.
<Ip,0
I.    Rated switch current--SwitcherCAD enters a value from
 the database for the IC it has selected. The LT1070/LT1170
 family current-mode ICs have switch-current ratings that
 decrease linearly for duty cycles above 50%. SwitcherCAD
 recomputes the maximum switch-current rating for the actual
 operating duty cycle to ensure that switch-current ratings
 are not exceeded. If this parameter is increased, SwitcherCAD
 may generate a design that exceeds data-sheet limits. Please
 be responsible, folks.
<Rsw,0
I.    Switch ON resistance--SwitcherCAD enters a value from
 the database for the IC it has selected, but to give more
 realistic results for efficiency, etc., it uses a value
 which may be slightly less than the worst-case-over-temperature
 specification.
<Vs,0
I.    Switch offset voltage loss--SwitcherCAD enters a value
 from the database for the IC it has selected. This parameter
 is the extrapolated voltage drop across the switch at zero
 switch current. It is zero for ICs in the LT1070/LT1170
 family, which use saturating switch designs. Emitter-follower
 switches like those used in the LT1074 and LT1076 will have
 a value of 0.5V to 1.5V.
<Fkhz,0
I.    Switching frequency--SwitcherCAD enters a value from
 the database for the IC it has selected. This parameter
 can be altered to check the effects of worst-case variations
 in frequency. Lower frequencies will increase peak device
 current levels, and higher frequencies will increase ac
 switching losses.
<DCmax,0
I.    Maximum duty cycle--SwitcherCAD enters a value from
 the database for the IC it has selected. This parameter
 may limit minimum input voltage.
<Vd,0
I.    Diode forward voltage used for calculations--To keep
 SwitcherCAD equations manageable, diode forward voltage
 is treated as a constant. This is reasonable if the value
 chosen represents the full-load condition. At lighter loads,
 efficiency will appear slightly lower, but if this is important,
 a new number can be inserted. If the diode's maximum reverse
 voltage is less than 40V, SwitcherCAD selects a Schottky
 diode with a forward voltage drop of 0.5V. Otherwise, a
 silicon diode is chosen, with a forward voltage drop of
 0.8V.
<CkHz_kGs,0
I.    Core loss constant (C)--This and the next three constants
 are used to describe inductor core material for calculating
 core loss. Appendix E describes how these constants are
 calculated. SwitcherCAD inserts numbers for Type 52 powdered-iron
 material. Be extremely careful when changing these numbers
 because even small errors here can result in large errors
 in calculated core loss.
<d,0
I.    Core loss frequency exponent (d)--See "Core loss constant,"
 above.
<p,0
I.    Core loss flux density exponent (p)--See "Core loss
 constant," above.
<U,0
I.    Core permeability (u)--See "Core loss constant," above.
<PctCuL,0
I.    Enter copper loss (% of Pout)--SwitcherCAD uses this
 number to calculate the maximum inductor series resistance
 needed to achieve the specified power loss at maximum load
 current. This number can be increased to yield smaller inductors
 or decreased for greater efficiency. If peak load current
 is significantly higher than normal load current, but the
 peak is of short duration (<10s), consider using a smaller
 inductor with higher resistance. Be careful to avoid saturation
 at peak load currents. Short-circuit conditions may cause
 destructive overheating in small inductors, so make informed
 decisions in this regard.
<ESRL,0
O.    Inductor resistance for copper loss--Calculated based
 on copper loss, see above.
<PctCLsug,0
O.    Suggested core loss--SwitcherCAD selects a core loss
 based upon maximum output power. The suggested core loss
 varies from 5% at 1 watt and below to 2% at ten watts and
 above. SwitcherCAD computes a minimum value of inductance
 to achieve this loss, using maximum input voltage, where
 core loss is highest, and type-52 powered iron material.
 See Appendix E for details.
<PctCL,0
I.    Enter desired core loss--If SwitcherCAD's selection
 for core loss (above) is unacceptable, change it here. SwitcherCAD
 uses this value for calculations.
<LminCoreVinH,0
O.    Min inductor needed for core loss--See "Suggested core
 loss," above.
<C65,0
O.    Min inductor needed for output power--SwitcherCAD computes
 the minimum value needed at full load to ensure that switch-current
 rating is not exceeded. For conservative designs, a 40%
 "fudge factor" has been added to the suggested inductance
 because the inductor's permeability changes with dc current
 levels. Maximum input voltage is used in the calculation
 because that is where peak inductor current is highest.
 The calculated value of inductance will often be tantalizing
 low, but may result in excessive core loss. A practical
 value will normally be somewhat higher to reduce core loss,
 avoid large switch currents, provide guardbands, etc.
<PLSug,0
O.    Suggested inductor--SwitcherCAD selects the larger
 of the two inductors above to meet both switch-current and
 core-loss requirements.
<PL,0
I.    Enter chosen inductor-SwitcherCAD will initially use
 a value chosen from the database that meets or exceeds both
 the suggested inductance value and the copper-loss requirement.
 If the database does not contain an appropriate value, the
 program selects a value of 1,000,000mH. The user may change
 the value at will. SwitcherCAD uses this value for actual
 operating condition calculations.
<PLRsel,0
I.    Enter inductor series resistance--SwitcherCAD initially
 enters the dc resistance of the inductor chosen above. If
 the program cannot find an appropriate inductor in the database
 (see above), it selects a inductor series resistance of
 0.
<C158,0
O.    Operating mode at full load current--"Cont" or "Discont"
 indicates whether the regulator is in continuous or discontinuous
 mode at full load current.
<DCvar1,0
O.    Duty cycle--SwitcherCAD calculates operating conditions,
 including duty cycle, at minimum input voltage. Duty cycles
 above 50% will affect maximum available load current when
 using current-mode switchers, such as the LT1070/LT1170
 families.
<IswMaxVinL,0
O.    Max rated switch current at this duty cycle--See above.
 Maximum available switch current drops about 0.67% for each
 1% increase in duty cycle above 50% for the LT1070/LT1170
 family regulators.
<ILpkVinL,0
O.    Peak inductor/switch current--This current must be
 lower than the maximum-rated switch-current limit (see above)
 in order to ensure that the IC is being operated within
 specifications.
<Icrit,0
O.    Output current at crossover--SwitcherCAD calculates
 the load current at which the regulator is operating at
 the boundary between continuous and discontinuous modes.
 At high input voltage, the regulator will shift to continuous
 mode at higher load currents. Unless transient response
 is critical, shifting to discontinuous mode does not affect
 the performance of the regulator.
<C163,0
O.    Is max switch current exceeded?--Peak switch current
 is compared to maximum-rated switch current at the operating
 duty cycle (see above) to ensure that the IC is being operated
 within its specifications. If the rated switch-current limit
 is exceeded, a "Yes" is displayed here. If this occurs,
 a larger inductor value or an IC with a higher switch current
 rating must be used.
<MaxDCe,0
O.    Is max duty cycle exceeded?--If the IC's maximum duty
 cycle has been exceeded, a "Yes" is displayed here. LTC
 switchers have a maximum duty cycle of 80%-90% depending
 on the particular part type. Maximum duty cycle limits minimum
 input voltage for the regulator. Refer to Table 3.2.2 for
 the ICs maximum duty cycle rating.
<ILRMSVinL,0
O.    RMS inductor current--The inductor's RMS current is
 usually slightly higher than its average current. The inductor's
 RMS current and its desired copper loss are used to determine
 wire size. Worst-case RMS current occurs at maximum input
 voltage.
<ILpkVinL,0
O.    Peak inductor current--The selected inductor must not
 saturate at this current level.
<ILIppVinL,0
O.    P-P inductor ripple current--Peak-to-peak inductor
 current is determined by switching frequency, input voltage,
 and inductance value. It determines inductor core loss.
 Larger value inductors will improve core loss but will be
 physically larger and more expensive. Worst-case core loss
 occurs at the maximum input voltage.
<C239,0
O.    Inductor V*us product--This is the product of voltage
 across an inductor and the time it is present. This product
 determines inductor ripple current, and therefore core loss.
 Inductor manufacturers often specify maximum volt'microsecond
 (V*us) products for their inductors to avoid excess heating
 due to core loss. This parameter is specified by the manufacturer
 at a particular frequency and the maximum limit must be
 adjusted for other frequencies.
<ICRMSVinL,0
O.    Input capacitor RMS ripple current--This is an extremely
 important parameter because it determines the physical size
 of the input capacitor, which may be one of the largest
 components in the regulator. Worst-case RMS capacitor current
 does not occur at the minimum input voltage. To "worst case"
 you must increase the minimum input voltage to 0.2(Vout).

    SwitcherCAD will select multiple capacitors from the
 database if the input capacitor's RMS ripple current exceeds
 the maximum ripple-current rating of the capacitors in the
 database. Paralleling allows sharing of the ripple current
 between capacitors. See Appendix A for further details.
<ICESRsel,0
I.    Enter input capacitor ESR--This value is used to calculate
 power loss in the input capacitor for efficiency calculations.
 If the database does not contain an appropriate filter capacitor,
 the program selects an ESR of 0.
<ICValsel,0
I.    Enter input capacitor value--The actual value of the
 input capacitor in microfarads is not important because
 the capacitor is purely resistive at switching frequencies.
 SwitcherCAD uses this value simply for the parts list printout.
 If the database does not contain an appropriate value, the
 program selects a value of 1,000,000mF.
<OCRMSVinL,0
O.    Output capacitor RMS ripple current--Ripple current
 in the output capacitor is much lower than in the input
 capacitor because it is filtered by the inductor. The output
 capacitor size may be determined by ripple current, but
 is often increased above this size to meet the output-ripple
 voltage specification.
<OCESRmax,0
O.    Output-capacitor ESR for ripple voltage--This is the
 ESR (effective series resistance) needed in the output capacitor
 to meet the ripple voltage specification without requiring
 an additional output filter. For low output-ripple specifications,
 the ESR may be unreasonably low and a filter will be needed.
 Keep in mind that electrolytic capacitor ESR is very temperature
 dependent, increasing dramatically at low temperatures.
<OCESRsel,0
I.    Enter output-capacitor ESR--Actual ESR of the chosen
 output capacitor can be entered here. If the database does
 not contain an appropriate value, the program selects an
 ESR of 0.
<OCValsel,0
I.    Enter output capacitor value--The actual value of the
 output capacitor in microfarads is not important, because
 the capacitor is assumed to be purely resistive at switching
 frequencies. SwitcherCAD uses this value simply for the
 parts list printout. If the database does not contain an
 appropriate value, the program selects a value of 1,000,000mF.
 Also, this value will be the sum of all capacitors if SwitcherCAD
 selects multiple capacitors to meet the RMS ripple current
 requirement (see parts list printout).
<VoppVinLvar1,0
O.    Output ripple (p-p) without filter--Ripple voltage
 is calculated using the ESR from above. Calculations are
 done at minimum input voltage, which is not the worst-case
 condition. To "worst case," you must increase the minimum
 input voltage to maximum input voltage. Don't forget that
 capacitor ESR increases significantly at low temperatures.
<OutFilterReq,0
O.    Is an output filter required?--The output-ripple voltage
 limit is compared to the output ripple without a filter
 (see above) and if the output-ripple voltage limit is exceeded,
 a "Yes" is displayed here.
<FilterAtt,0
O.    Filter attenuation ratio needed--If an output filter
 is needed, SwitcherCAD divides the unfiltered output ripple
 by the specified output voltage ripple to obtain the required
 attenuation.
<FCCdata,0
O.    Suggested Filter Capacitance from database--SwitcherCAD
selects a filter capacitor using the formula 40uF(IOutMax + 0.5). This
 formula is a rule of thumb used by LTC and represents a compromise
 between capacitor size and regulator transient response.
 The capacitance is used only for calculating the filter's
 resonant frequency.
<FCC,0
I.    Enter Filter Capacitance --SwitcherCAD enters the
selected database capacitor here (see above). This value can be
changed if an alternate capacitor is selected. The
capacitance value is used only for calculating the filter's
 resonant frequency.
<FCESRdata,0
O.    Enter filter capacitor ESR--SwitcherCAD enters the
 chosen capacitor's ESR (see above). For sudden changes in
 load current the ESR of this capacitor allows the output
 voltage to shift. If the output voltage variation is unacceptable,
 then a capacitor with lower ESR should be chosen. Refer
 to the LC output filter section for further details.
<FCESRsel1,0
I.    Enter filter capacitor ESR--SwitcherCAD enters the
selected database capacitor ESR here (see above). This value can be
changed if an alternate capacitor is selected.
<FLmin,0
O.    L needed for output ripple--This is the inductance
 value required to obtain the calculated filter attenuation.
 Rod- or drum-shaped inductors may be substituted for more
 expensive toroids in the LC output filter, because ripple
 current is usually low enough to avoid magnetic-field radiation
 problems.
<FLsel,0
I.    Enter actual L selected--SwitcherCAD selects the smallest
 inductor in the database that has the required inductance
 and is rated to handle full load current.
<C193,0
O.    Output ripple voltage after filter--Actual output ripple
 is calculated using the LC filter capacitor ESR and the
 inductance selected above.
<C195,0
O.    Resonant frequency of filter--This frequency is calculated
 to allow comparison to the frequencies of dynamic loads.
 At the resonant frequency, the filter's output impedance
 is at its maximum.
<C193,4
O.    Output ripple voltage after filter--Actual output ripple
 is calculated using the LC filter capacitor ESR and the
 inductance selected above.
<C195,4
O.    Resonant frequency of filter--This frequency is calculated
 to allow comparison to the frequencies of dynamic loads.
 At the resonant frequency, the filter's output impedance
 is at its maximum.
<IpkVinL,0
O.    Peak switch current--transferred from a previous line
 and displayed here for informational purposes.
<IswAvgVinL,0
O.    Average switch current during on-time--The worst-case
 condition occurs at the minimum input voltage.
<PIC,0
O.    Power dissipated in IC--This is the total power dissipated
 in the IC, including power from quiescent current, switch-on
 voltage, switch rise and fall times, and the switch driver.
 For the LT1074/LT1076 family, the worst-case condition normally
 occurs at the minimum input voltage, because switch-conduction
 losses dominate IC dissipation. At higher input voltages
 switch ac loss can become significant for the LT1074/LT1076
 family.
<TjICMax,0
O.    Maximum-rated IC junction temperature--Transferred
 from the Design Specification screen.
<ThetaJAIC,0
I.    Thermal resistance of IC JA--Junction-to-ambient thermal
 resistance is transferred from the database. No external
 heatsink is assumed.
<ThetaJCIC,0
I.    Thermal resistance of IC JC--Junction-to-case thermal
 resistance is transferred from the database.
<C209,0
O.    Is an IC heatsink required?--IC junction temperature
 is calculated assuming no external heatsink. If the maximum
 junction temperature is exceeded, a "Yes" is displayed here
 and a heat sink must be added in order to meet the IC's
 maximum junction-temperature requirement.
<RICThetaCA,0
O.    Max thermal resistance of IC heatsink--If a heatsink
 is required, SwitcherCAD calculates the heatsink thermal
 resistance using IC power dissipation and junction-to-case
 thermal resistance. This heatsink is the bare minimum required
 for reliable operation, and will result in the IC operating
 at its maximum-rated junction temperature. We strongly recommend
 that a larger heatsink be used if the regulator is expected
 to operate at maximum load current for extended periods.
<ThetaCAICHS,0
I.    Enter thermal resistance of heatsink--The value calculated
 above is initially displayed here, but the user should enter
 the actual value for the selected heatsink.
<TIC,0
O.    IC temperature at max ambient temperature--IC-junction
 temperature is calculated using the actual heatsink thermal
 resistance entered above.
<IdAvgVinL,0
O.    Average diode current--For the buck topology, the average
 diode current is less than the output current. This current
 is at its maximum at high input voltage, not at minimum
 input voltage where SwitcherCAD calculates operating conditions.
 The user should increase minimum input voltage to the maximum
 figure to check worst-case diode current. SwitcherCAD selects
 the minimum current rating of the diode by adding the selected
 IC's switch-current rating to the output current and dividing
 the result by two as a compromise between normal and short
 circuit conditions.
<C215,4
O.    Average diode current--For the buck topology, the average
 diode current is less than the output current. This current
 is at its maximum at high input voltage, not at minimum
 input voltage where SwitcherCAD calculates operating conditions.
 The user should increase minimum input voltage to the maximum
 figure to check worst-case diode current. SwitcherCAD selects
 the minimum current rating of the diode by adding the selected
 IC's switch-current rating to the output current and dividing
 the result by two as a compromise between normal and short
 circuit conditions.
<IdpkVinL,0
O.    Peak diode current--Peak diode current is the sum of
 output current and one-half of the peak-to-peak inductor
 ripple current. This is included primarily for informational
 purposes.
<IdAvgOnVinL,0
O.    Average diode current during on-time--For this topology,
 it is equal to the output current. "On-time" refers to the
 period when the diode is conducting, rather than to switch-on
 time. The worst case condition occurs at the maximum input
 voltage.
<C217,4
O.    Average diode current during on-time--For this topology,
 it is equal to the output current. "On-time" refers to the
 period when the diode is conducting, rather than to switch-on
 time. The worst case condition occurs at the maximum input
 voltage.
<IdVrmaxVinH,0
O.    Max diode reverse voltage @VinH--For this topology
 it is equal to the maximum input voltage.
<C221,0
O.    Suggested diode type--If the diode's maximum reverse
 voltage is less than 40V SwitcherCAD selects a Schottky
 diode with a forward voltage drop of 0.5V. Otherwise, a
 silicon diode is chosen with a forward voltage drop of 0.8V.
<Vf,0
I.    Diode forward voltage for thermal calc--The forward
 voltage drop of most diodes operating at high current densities
 decreases as ambient temperature is increased, at a rate
 of approximately -1mV/oC. To do a "worst-case" analysis
 of a diode's junction temperature, use the actual diode
 forward voltage drop at the maximum operating temperature;
 otherwise the calculated temperature will be artificially
 high. Enter a number here which represents the diode's high-temperature
 forward voltage at a current equal to the output current.
 Refer to Appendix D for further details.
<Trr,0
I.    Diode reverse recovery time--If a Schottky diode is
 chosen, the recovery time is assumed to be zero. Otherwise,
 for a silicon diode, SwitcherCAD enters the value from its
 database for the chosen diode.
<Pdiod,0
O.    Power dissipated in diode--This is the sum of forward
 losses and reverse-recovery losses. SwitcherCAD assumes
 that all reverse-recovery loses are dissipated in the diode,
 whereas in actual operation, some of the losses may be transferred
 to the IC. In SwitcherCAD, the worst-case diode dissipation
 occurs at the maximum input voltage.
<TjDMax,0
O.    Max rated diode junction temperature--Transferred from
 the Design Specification screen.
<ThetaJAD,0
I.    Thermal resistance of diode JA--This number is transferred
 from the database and assumes no heatsink. Enter the appropriate
 figure if the diode type is changed.
<ThetaJCD,0
I.    Thermal resistance of diode JC--This number is transferred
 from the database and assumes no heatsink. Enter the appropriate
 figure if the diode type is changed.
<C230,0
O.    Is a diode heatsink required?--Diode junction temperature
 is calculated assuming no external heatsink. If the maximum
 junction temperature is exceeded, a "Yes" is displayed here
 and a heatsink must be added in order to meet the diode's
 maximum junction-temperature requirement. Diode thermal
 resistance is critically dependent on mounting technique,
 especially for axial-lead diodes. Some manufacturers unrealistically
 assume ideal mounting conditions when specifying diode thermal
 resistance. Always consult the diode data sheet carefully
 before committing to a diode type and/or mounting procedure.
<RDThetaCA,0
O.    Maximum thermal resistance of diode heatsink--If a
 heatsink is required SwitcherCAD enters the maximum thermal
 resistance based on maximum ambient temperature and junction-to-case
 thermal resistance. In buck converters, it is sometimes
 convenient for the diode and IC to share a heatsink, because
 power shifts from one to the other as the input voltage
 varies, and they are never dissipate the most heat at the
 same time. If you do this, take care to maintain electrical
 isolation.
<ThetaCADHS,0
I.    Enter thermal resistance of diode heatsink--The value
 calculated above is initially displayed here, but the user
 should enter the actual value for the selected heatsink.
<TD,0
O.    Diode temperature at maximum ambient temperature--The
 diode temperature is calculated at minimum input voltage,
 using the actual value for the heatsink entered in the previous
 line.
<Dummy2
(Positive-to-Negative Buck-Boost and Negative-to-Positive
 Buck-Boost)

<vout,2
I.    Main Output Voltage--This value is transferred from
 the Design Specification screen, but you can change it here
 if you wish.
<vinmin,2
I.    Minimum input voltage--This value is transferred from
 the Design Specification screen. You should definitely change
 the minimum input voltage as part of the design procedure,
 because SwitcherCAD calculates detailed operating conditions
 only at minimum input voltage. This was done because, for
 many topologies, minimum input voltage represents a worst-case
 current condition for most of the components. In a buck-boost
 converter, switch, diode, inductor and input and output
 filter capacitor dissipation are highest at low Vin. Ac
 losses in the IC switch and diode are highest at the maximum
 input voltage Refer to Table 5.2.1 for worst-case operating
 conditions for each power component.
<vinnom,2
I.    Nominal input voltage--This input was originally included
 in SwitcherCAD as a condition for calculating efficiency.
 It was dropped from use when the program run time became
 too long, but remains available for future use.
<vinmax,2
I.    Maximum input voltage--Maximum input voltage is used
 only to calculate worst-case voltage conditions for the
 IC, catch diode, and input capacitor.
<ioutmin,2
I.    Minimum load current--This parameter is not used in
 the buck-boost converter program. All buck-boost designs
 supported by SwitcherCAD operate down to zero load current.
 They will begin to operate in discontinuous mode when load
 current drops low enough, and SwitcherCAD calculates this
 point for reference.
<ioutnom,2
I.    Nominal load current--Not used. See "Nominal input
 voltage."
<ioutmax,2
I.    Maximum load current--SwitcherCAD calculates operating
 conditions at maximum load current only, so this parameter
 can be modified to observe the effects of load changes on
 various parameters.
<DVopp,2
I.    Output-ripple voltage--Ripple voltage is specified
 by the user, and SwitcherCAD tries to create a design which
 meets this specification without using an additional output
 filter. However, If SwitcherCAD decides that the output
 capacitor would be unreasonably large, it adds an output
 filter and computes values to meet the ripple specification.
 The user should carefully examine the resulting design to
 see if human intelligence judicially applied could shift
 inductor, capacitor, and frequency values to meet the ripple
 specification more effectively or economically. Many times,
 a low ripple voltage is rather arbitrarily chosen, and a
 little hard-nosed investigation will show that the load
 will actually tolerate more ripple. If this eliminates the
 need for the additional filter, everyone wins.
<tamax,2
I.    Max ambient temperature--This parameter is used to
 calculate the amount of heatsinking required for the IC,
 catch diode, and filter capacitors. Remember that SwitcherCAD
 calculates the minimum amount of heatsinking required to
 keep junction temperature below maximum specification. Conservative
 design suggests some guardbanding here.
    When selecting filter capacitors, SwitcherCAD assumes
 maximum ambient temperature and a 20,000 hour required lifetime.
 If SwitcherCAD cannot find a filter capacitor in its database
 to satisfy the lifetime requirement, it will default to
 a 1,000,000mF capacitor. The database contains aluminum
 electrolytic capacitors rated at 105°C. If SwitcherCAD does
 not find a suitable capacitor, then you should select an
 alternate capacitor technology (e.g., Sanyo OS-CON's), use
 paralleled units, or lower the lifetime requirement and
 use the equation in Appendix A to determine the proper filter
 capacitor.
<VswM,2
I.    Maximum-rated switch voltage--SwitcherCAD enters a
 value from the database for the IC it has selected. This
 can be altered for special purposes, but if it is increased
 the resulting design may violate LTC's data-sheet specifications.
 It is the user's responsibility to ensure that the IC is
 not subjected to over-voltage conditions.
<Ip,2
I.    Rated switch current--SwitcherCAD enters a value from
 the database for the IC it has selected. The LT1070/LT1170
 family current-mode ICs have switch-current ratings that
 decrease linearly for duty cycles above 50%. SwitcherCAD
 recomputes the maximum switch-current rating for the actual
 operating duty cycle to ensure that switch-current ratings
 are not exceeded. If this parameter is increased, SwitcherCAD
 may generate a design that exceeds data-sheet limits. Please
 be responsible, folks.
<Rsw,2
I.    Switch on resistance--SwitcherCAD enters a value from
 the database for the IC it has selected, but to give more
 realistic results for efficiency, etc., it uses a value
 which may be slightly less than the worst-case-over-temperature
 specification.
<Vs,2
I.    Switch offset voltage loss--SwitcherCAD enters a value
 from the database for the IC it has selected. This parameter
 is the extrapolated voltage drop across the switch at zero
 switch current. It is zero for ICs in the LT1070/LT1170
 family, which use saturating switch designs. Emitter-follower
 switches like those used in the LT1074 and LT1076 will have
 a value of 0.5V to 1.5V.
<Fkhz,2
I.    Switching frequency--SwitcherCAD enters a value from
 the database for the IC it has selected. This parameter
 can be altered to check the effects of worst-case variations
 in frequency. Lower frequencies will increase peak device
 current levels, and higher frequencies will increase ac
 witching losses.
<DCmax,2
I.    Maximum duty cycle--SwitcherCAD enters a value from
 the database for the IC it has selected. This parameter
 may limit minimum input voltage.
<Vd,2
I.    Diode forward voltage used for calculations--To keep
 SwitcherCAD equations manageable, diode forward voltage
 is treated as a constant. This is reasonable if the value
 chosen represents the full-load condition. At lighter loads,
 efficiency will appear slightly lower, but if this is important,
 a new number can be inserted. If the diode's maximum reverse
 voltage is less than 40V, SwitcherCAD selects a Schottky
 diode with a forward voltage drop of 0.5V. Otherwise, a
 silicon diode is chosen, with a forward voltage drop of
 0.8V.
<CkHz_kGs,2
I.    Core loss constant (C)--This and the next three constants
 are used to describe inductor core material for calculating
 core loss. Appendix E describes how these constants are
 calculated. SwitcherCAD inserts numbers for Type 52 powdered-iron
 material. Be extremely careful when changing these numbers
 because even small errors here can result in large errors
 in calculated core loss.
<d,2
I.    Core loss frequency exponent (d)--See "Core loss constant,"
 above.
<p,2
I.    Core loss flux density exponent (p)--See "Core loss
 constant," above.
<U,2
I.    Core permeability (u)--See "Core loss constant," above.
<PctCuL,2
I.    Enter copper loss (% of Pout)--SwitcherCAD uses this
 number to calculate the maximum inductor series resistance
 needed to achieve the specified power loss at maximum load
 current. This number can be increased to yield smaller inductors
 or decreased for greater efficiency. If peak load current
 is significantly higher than normal load current, but the
 peak is of short duration (<10s), consider using a smaller
 inductor with higher resistance, but be careful to avoid
 saturation at peak load currents. Short-circuit conditions
 may cause destructive overheating in small inductors, so
 make informed decisions in this regard.
<ESRL,2
O.    Inductor resistance for copper loss--Calculated based
 on copper loss, see above.
<PctCLsug,2
O.    Suggested core loss--SwitcherCAD selects a core loss
 based upon maximum output power. The suggested core loss
 varies from 5% at 1 watt and below to 2% at ten watts and
 above. It then computes a minimum value of inductance to
 achieve this loss, using maximum input voltage, where core
 loss is highest, and type 52 powdered iron material. See
 Appendix E for details.
<PctCL,2
I.    Enter desired core loss--If SwitcherCAD's selection
 for core loss (above) is unacceptable, change it here. SwitcherCAD
 uses this value for calculations.
<LminCoreVinH,2
O.    Min inductor needed for core loss--See Suggested core
 loss (above).
<C76,2
O.    Min inductor needed for output power--SwitcherCAD computes
 the minimum value needed at full load to ensure that switch-current
 rating is not exceeded. For conservative designs, a 40%
 "fudge factor" has been added to the suggested inductance
 because the inductor's permeability changes with dc current
 levels. Minimum input voltage is used in the calculation
 because that is where peak inductor current is highest.
 The calculated value of inductance will often be tantalizing
 low, but may result in excessive core loss. A practical
 value will normally be somewhat higher to reduce core loss,
 avoid large switch currents, provide guardbands, etc.
<C77,6
O.    Min inductor needed for output power--SwitcherCAD computes
 the minimum value needed at full load to ensure that switch-current
 rating is not exceeded. For conservative designs, a 40%
 "fudge factor" has been added to the suggested inductance
 because the inductor's permeability changes with dc current
 levels. Minimum input voltage is used in the calculation
 because that is where peak inductor current is highest.
 The calculated value of inductance will often be tantalizing
 low, but may result in excessive core loss. A practical
 value will normally be somewhat higher to reduce core loss,
 avoid large switch currents, provide guardbands, etc.
<PLSug,2
O.    Suggested inductor--SwitcherCAD selects the larger
 of the two inductors above to meet both switch-current and
 core-loss requirements.
<PL,2
I.    Enter chosen inductor-SwitcherCAD will initially use
 a value chosen from the database that meets or exceeds both
 the suggested inductance value and the copper-loss requirement.
 If the database does not contain an appropriate value, the
 program selects a value of 1,000,000mH. The user may change
 the value at will. SwitcherCAD uses this value for actual
 operating condition calculations.
<PLRsel,2
I.    Enter inductor series resistance--SwitcherCAD initially
 enters the dc resistance of the inductor chosen above. If
 the program cannot find an appropriate inductor in the database
 (see above), it selects a inductor series resistance of
 0.
<C181,2
O.    Operating mode at full load current--"Cont" or "Discont"
 indicates whether the regulator is in continuous or discontinuous
 mode at full load current.
<DCvar1,2
O.    Duty cycle--SwitcherCAD calculates operating conditions,
 including duty cycle, at minimum input voltage. Duty cycles
 above 50% will affect maximum available load current when
 using current-mode switchers, such as the LT1070/LT1170
 family.
<IswMaxVinL,2
O.    Max rated switch current at this duty cycle--See above.
 Maximum available switch current drops about 0.67% for each
 1% increase in duty cycle above 50% for the LT1070/LT1170
 family regulators.
<ILpkVinL,2
O.    Peak inductor/switch current--This current must be
 lower than the maximum-rated switch-current limit (see above)
 in order to ensure that the IC is being operated within
 specifications. The peak switch current can be much higher
 than the output current with low values of Vin.
<Icrit,2
O.    Output current at crossover--SwitcherCAD calculates
 the load current at which the regulator is operating at
 the boundary between continuous and discontinuous modes.
 At high input voltage, the regulator will shift to continuous
 mode at higher load currents. Unless transient response
 is critical, shifting to discontinuous mode does not affect
 the performance of the regulator.
<C186,2
O.    Is max switch current exceeded?--Peak switch current
 is compared to maximum-rated switch current at the operating
 duty cycle (see above) to ensure that the IC is being operated
 within its specifications. If the rated switch-current limit
 is exceeded, a "Yes" is displayed here. If this occurs,
 a larger inductor value or an IC with a higher switch current
 rating must be used. The peak switch current can be much
 higher than the output current with low values of Vin.
<MaxDCe,2
O.    Is max duty cycle exceeded?--If the IC's maximum duty
 cycle has been exceeded, a "Yes" is displayed here. LTC
 switchers have a maximum duty cycle of 80%-90% depending
 on the particular part type. Maximum duty cycle limits minimum
 input voltage for the regulator. Refer to Table 3.3.2 for
 the ICs maximum duty cycle rating.
Inductor Operating Conditions
<ILRMSVinL,2
O.    RMS inductor current--The inductor's RMS current is
 usually slightly higher than its average current. The inductor's
 RMS current and its desired copper loss are used to determine
 wire size. Worst-case RMS current occurs at minimum input
 voltage.
<ILpkVinL,2
O.    Peak inductor current--The selected inductor must not
 saturate at this current level.
<ILIppVinL,2
O.    P-P inductor ripple current--Peak-to-peak inductor
 current is determined by switching frequency, input voltage,
 and inductance value. It determines inductor core loss.
 Larger value inductors will improve core loss but will be
 physically larger and more expensive. Worst-case core loss
 occurs at the maximum input voltage.
<C259,2
O.    Inductor V*us product--This is the product of voltage
 across an inductor and the time it is present. This product
 determines inductor ripple current, and therefore core loss.
 Inductor manufacturers often specify maximum volt'microsecond
 (V*us) product for their inductors to avoid excess heating
 due to core loss. This parameter is specified by the manufacturer
 at a particular frequency and the maximum limit must be
 adjusted for other frequencies.
<ICRMSVinL,2
O.    Input capacitor RMS ripple current--This is an extremely
 important parameter because it determines the physical size
 of the input capacitor, which may be one of the largest
 components in the regulator. Worst case RMS capacitor current
 occurs at the minimum input voltage.
    SwitcherCAD will select multiple capacitors from the
 database if the input capacitor's RMS ripple current exceeds
 the maximum ripple-current rating of the capacitors in the
 database. Paralleling allows sharing of the ripple current
 between capacitors. See Appendix A for further details.
<ICESRsel,2
I.    Enter input capacitor ESR--This value is used to calculate
 power loss in the input capacitor for efficiency calculations.
 If the database does not contain an appropriate filter capacitor,
 the program selects an ESR of 0.
<ICValsel,2
I.    Enter input capacitor value--The actual value of the
 input capacitor in microfarads is not important, because
 the capacitor is purely resistive at switching frequencies.
 SwitcherCAD uses this value simply for the parts list printout.
 If the database does not contain an appropriate value, the
 program selects a value of 1,000,000uF.
<OCRMSVinL,2
O.    Output capacitor RMS ripple current--This is an extremely
 important parameter because it determines the physical size
 of the output capacitor, which may be one of the largest
 components in the regulator. Worst case output capacitor
 RMS ripple current occurs at the minimum input voltage.

    SwitcherCAD will select multiple capacitors from the
 database if the output capacitor's RMS ripple current exceeds
 the maximum ripple-current rating of the capacitors in the
 database. Paralleling allows sharing of the ripple current
 between capacitors. See Appendix A for further details.
<OCESRmax,2
O.    Output-capacitor ESR for ripple voltage--This is the
 ESR (effective series resistance) needed in the output capacitor
 to meet the ripple voltage specification without requiring
 an additional output filter. For low output-ripple specifications,
 the ESR may be unreasonably low and a filter will be needed.
 Keep in mind that electrolytic capacitor ESR is very temperature
 dependent, increasing dramatically at low temperatures.
<OCESRsel,2
I.    Enter output-capacitor ESR--Actual ESR of the chosen
 output capacitor can be entered here. If the database does
 not contain an appropriate value, the program selects an
 ESR of 0.
<OCValsel,2
I.    Enter output capacitor value--The actual value of the
 output capacitor in microfarads is not important, because
 the capacitor is assumed to be purely resistive at switching
 frequencies. SwitcherCAD uses this value simply for the
 parts list printout. If the database does not contain an
 appropriate value, the program selects a value of 1,000,000uF.
 Also, this value will be the sum of all capacitors if SwitcherCAD
 selects multiple capacitors to meet the RMS ripple current
 requirement (See parts list printout).
<VoppVinLvar1,2
O.    Output ripple (p-p) without filter--Ripple voltage
 is calculated using the ESR from above. Calculations are
 done at minimum input voltage, which is the worst-case condition
 for output ripple in this topology. Don't forget that capacitor
 ESR increases significantly at low temperatures.
<OutFilterReq,2
O.    Is an output filter required?--The output-ripple voltage
 limit is compared to the output ripple without a filter
 (see above) and if the output-ripple voltage limit is exceeded,
 a "Yes" is displayed here.
<FilterAtt,2
O.    Filter attenuation ratio needed--If an output filter
 is needed, SwitcherCAD divides the unfiltered output ripple
 by the specified output voltage ripple to obtain the required
 attenuation.
<FCCdata,2
O.    Suggested Filter Capacitance from database--SwitcherCAD
selects a filter capacitor using the formula 40uF(IOutMax + 0.5). This
 formula is a rule of thumb used by LTC and represents a compromise
 between capacitor size and regulator transient response.
 The capacitance is used only for calculating the filter's
 resonant frequency.
<FCC,2
I.    Enter Filter Capacitance --SwitcherCAD enters the
selected database capacitor here (see above). This value can be
changed if an alternate capacitor is selected. The
capacitance value is used only for calculating the filter's
 resonant frequency.
<FCESRdata,2
O.    Enter filter capacitor ESR--SwitcherCAD enters the
 chosen capacitor's ESR (see above). For sudden changes in
 load current the ESR of this capacitor allows the output
 voltage to shift. If the output voltage variation is unacceptable,
 then a capacitor with lower ESR should be chosen. Refer
 to the LC output filter section for further details.
<FCESRsel1,2
I.    Enter filter capacitor ESR--SwitcherCAD enters the
selected database capacitor ESR here (see above). This value can be
changed if an alternate capacitor is selected.
<FLmin,2
O.    L needed for output ripple--This is the inductance
 value required to obtain the calculated filter attenuation.
 Rod- or drum-shaped inductors may be substituted for more
 expensive toroids in the LC output filter, because ripple
 current is usually low enough to avoid magnetic-field radiation
 problems.
<FLsel,2
I.    Enter actual L selected--SwitcherCAD selects the smallest
 inductor in the database that has the required inductance
 and is rated to handle full load current.
<C216,2
O.    Output ripple voltage after filter--Actual output ripple
 is calculated using the LC filter capacitor ESR and the
 inductance selected above.
<C218,2
O.    Resonant frequency of filter--This frequency is calculated
 to allow comparison to the frequencies of dynamic loads.
 At the resonant frequency, the filter's output impedance
 is at its maximum.
<C216,6
O.    Output ripple voltage after filter--Actual output ripple
 is calculated using the LC filter capacitor ESR and the
 inductance selected above.
<C218,6
O.    Resonant frequency of filter--This frequency is calculated
 to allow comparison to the frequencies of dynamic loads.
 At the resonant frequency, the filter's output impedance
 is at its maximum.
<IpkVinL,2
O.    Peak switch current--transferred from a previous line
 and displayed here for informational purposes.
<IswAvgVinL,2
O.    Average switch current during on-time--The worst-case
 condition occurs at the minimum input voltage.
<PIC,2
O.    Power dissipated in IC--This is the total power dissipated
 in the IC, including power from quiescent current, switch-on
 voltage, switch rise and fall times, and the switch driver.
 The worst-case condition normally occurs at the minimum
 input voltage, because switch-conduction usually losses
 dominate IC dissipation. At maximum input voltage the ac
 loss can become significant for the LT1074 family.
<TjICMax,2
O.    Maximum-rated IC junction temperature--Transferred
 from the Design Specification screen.
<ThetaJAIC,2
I.    Thermal resistance of IC JA--Junction-to-ambient thermal
 resistance is transferred from the database. No external
 heatsink is assumed.
<ThetaJCIC,2
I.    Thermal resistance of IC JC--Junction-to-case thermal
 resistance is transferred from the database.
<C231,2
O.    Is an IC heatsink required?--IC junction temperature
 is calculated assuming no external heatsink. If the maximum
 junction temperature is exceeded, a "Yes" is displayed here
 and a heatsink must be added in order to meet the IC's maximum
 junction-temperature requirement.
<RICThetaCA,2
O.    Max thermal resistance of IC heatsink--If a heatsink
 is required, SwitcherCAD calculates the heatsink thermal
 resistance using IC power dissipation and junction-to-case
 thermal resistance. This heatsink is the bare minimum required
 for reliable operation, and will result in the IC operating
 at its maximum-rated junction temperature. We strongly recommend
 that a larger heatsink be used if the regulator is expected
 to operate at maximum load current for extended periods.
<ThetaCAICHS,2
I.    Enter thermal resistance of heatsink--The value calculated
 above is initially displayed here, but the user should enter
 the actual value for the selected heatsink.
<TIC,2
O.    IC temperature at max ambient temperature--IC-junction
 temperature is calculated using the actual heatsink thermal
 resistance entered above.
<C237,2
O.    Average diode current--For this topology the average
 diode current is equal to the output current and independent
 of input voltage, but peak diode current (see below) can
 be many times higher.
<IdpkVinL,2
O.    Peak diode current--Peak diode current is the sum of
 average current during switch on-time and one-half of the
 peak-to-peak inductor ripple current. This is included primarily
 for informational purposes.
<C239,2
O.    Average diode current during on time--In this case,
 "on time" refers to the period when the diode is conducting,
 rather than to switch on-time. Diode current during this
 period can be much higher than load current, so caution
 must be used in selecting the diode. SwitcherCAD selects
 an output diode current rating by adding the average diode
 current during on-time to the output current and then dividing
 the result by two. The worst-case condition occurs at the
 minimum input voltage.
<IdVrmaxVinH,2
O.    Max diode reverse voltage @VinH--For this topology
 it is equal to the maximum input voltage plus the output
 voltage.
<C241,2
O.    Suggested diode type--If the diode's maximum reverse
 voltage is less than 40V SwitcherCAD selects a Schottky
 diode with a forward voltage drop of 0.5V. Otherwise, a
 silicon diode is chosen with a forward voltage drop of 0.8V.
<Vf,2
I.    Diode forward voltage for thermal calc--The forward
 voltage drop of many diodes operating at high current densities
 decreases as ambient temperature is increased, at a rate
 of approximately -1mV/oC. To do a "worst-case" analysis
 of diode's junction temperature, use the actual diode forward
 voltage drop at the maximum operating temperature; otherwise
 the calculated temperature will be artificially high. Enter
 a number here which represents the diode's high-temperature
 forward voltage at a current equal to the average diode
 current during on-time.
    SwitcherCAD indicates that diode dissipation is independent
 of input voltage, because the program assumes a fixed value
 for the diode forward voltage and because average diode
 current is always equal to output current. Actually, diode
 dissipation will be somewhat lower at maximum input voltage,
 because peak diode current is lower and therefore Vf is
 lower. Refer to Appendix D for further details.
<Trr,2
I.    Diode reverse recovery time--If a Schottky diode is
 chosen, the recovery time is assumed to be zero. Otherwise,
 for a silicon diode, SwitcherCAD enters the value from its
 database for the chosen diode.
<Pdiod,2
O.    Power dissipated in diode--This is the sum of forward
 losses and reverse-recovery losses. SwitcherCAD assumes
 that all reverse-recovery loses are dissipated in the diode,
 whereas in actual operation, some of the losses may be transferred
 to the IC. In SwitcherCAD, schottky diode dissipation is
 independent of input voltage because the program assumes
 a constant forward voltage. It then multiplies this by the
 average current, which is always equal to output current.
 Reverse recovery losses are zero. With silicon diodes, forward
 losses are also treated as constant, but reverse recovery
 losses increase at high input voltages. In actual applications,
 both diode types show higher forward losses at low input
 voltages, because the average diode current during diode
 on time is higher and the real value for forward voltage
 increases.
<TjDMax,2
O.    Max rated diode junction temperature--Transferred from
 the Design Specification screen.
<ThetaJAD,2
I.    Thermal resistance of diode JA--This number is transferred
 from the database and assumes no heatsink. Enter the appropriate
 figure if the diode type is changed.
<ThetaJCD,2
I.    Thermal resistance of diode JC--This number is transferred
 from the database. Enter the appropriate figure if the diode
 type is changed.
<C250,2
O.    Is a diode heatsink required?--Diode junction temperature
 is calculated assuming no external heatsink. If the maximum
 junction temperature is exceeded, a "Yes" is displayed here
 and a heatsink must be added in order to meet the diode's
 maximum junction-temperature requirement. Diode thermal
 resistance is critically dependent on mounting technique,
 especially for axial-lead diodes. Some manufacturers unrealistically
 assume ideal mounting conditions when specifying diode thermal
 resistance. Always consult the diode data sheet carefully
 before committing to a diode type and/or mounting procedure.
<RDThetaCA,2
O.    Maximum thermal resistance of diode heatsink--If a
 heatsink is required SwitcherCAD enters the maximum thermal
 resistance based on maximum ambient temperature and junction-to-case
 thermal resistance
<ThetaCADHS,2
I.    Enter thermal resistance of diode heatsink--The value
 calculated above is initially displayed here, but the user
 should enter the actual value for the selected heatsink.
<TD,2
O.    Diode temperature at maximum ambient temperature--Diode
 temperature is calculated at minimum input voltage, using
 the actual value for the heatsink entered in the previous
 line.
<Dummy35.3 Boost (Positive Boost and Negative Boost)

<vout,1
I.    Main Output Voltage--This value is transferred from
 the Design Specification screen, but you can change it here
 if you wish.
<vinmin,1
I.    Minimum input voltage--This value is transferred from
 the Design Specification screen. You should definitely change
 the minimum input voltage as part of the design procedure,
 because SwitcherCAD calculates detailed operating conditions
 only at minimum input voltage. This was done because, for
 many topologies, minimum input voltage represents a worst-case
 current condition for most of the components. In a boost
 converter, switch, diode, and output capacitor dissipation
 are highest at low Vin, but input filter capacitor and inductor
 core losses are highest at Vin=0.5'(VOUT). Also, the IC
 and diode ac losses are highest at the maximum input voltage.
 Refer to Table 5.3.1 for worst-case operating conditions
 for each power component.
<vinnom,1
I.    Nominal input voltage--This input was originally included
 in SwitcherCAD as a condition for calculating efficiency.
 It was dropped from use when the program run time became
 too long, but remains for future use.
<vinmax,1
I.    Maximum input voltage--Maximum input voltage is used
 only to calculate worst-case voltage conditions for the
 IC and the input capacitor.
<ioutmin,1
I.    Minimum load current--This parameter is not used in
 the boost converter program. All boost designs supported
 by SwitcherCAD operate down to zero load current. They will
 begin to operate in discontinuous mode when load current
 drops low enough, and SwitcherCAD calculates this point
 for reference.
<ioutnom,1
I.    Nominal load current--Not used. See "Nominal input
 voltage."
<ioutmax,1
I.    Maximum load current--SwitcherCAD calculates operating
 conditions at maximum load current only, so this parameter
 can be modified to observe the effects of load changes on
 various parameters.
<DVopp,1
I.    Output ripple voltage--Ripple voltage is specified
 by the user, and SwitcherCAD tries to create a design which
 meets this specification without using an additional output
 filter. However, If SwitcherCAD decides that the output
 capacitor would be unreasonably large, it adds an output
 filter and computes values to meet the ripple specification.
 The user should carefully examine the resulting design to
 see if human intelligence judicially applied can shift inductor,
 capacitor, and frequency values to meet the ripple specification
 more effectively or economically. Many times, a low ripple
 voltage is rather arbitrarily chosen, and a little hard-nosed
 investigation will show that the load will actually tolerate
 more ripple. If this eliminates the need for the additional
 filter, everyone wins.
<tamax,1
I.    Maximum ambient temperature--This parameter is used
 to calculate the amount of heatsinking required for the
 IC, catch diode, and filter capacitors. Remember that SwitcherCAD
 calculates the minimum amount of heatsinking required to
 keep junction temperature below maximum specification. Conservative
 design suggests some guardbanding here.
    When selecting capacitors, SwitcherCAD assumes maximum
 ambient temperature and a 20,000 hour required lifetime.
 If SwitcherCAD cannot find a filter capacitor in its database
 to satisfy the lifetime requirement, it will default to
 a 1,000,000mF capacitor. The database contains aluminum
 electrolytic capacitors rated at 105°C. If SwitcherCAD does
 not find a suitable capacitor, then you should select an
 alternate capacitor technology (e.g., Sanyo OS-CON's), use
 paralleled units, or lower the lifetime requirement and
 use the equation in Appendix A to determine the proper filter
 capacitor.
<VswM,1
I.    Maximum-rated switch voltage--SwitcherCAD enters a
 value from the database for the IC it has selected. This
 can be altered for special purposes, but if it is increased
 the resulting design may violate LTC's data-sheet specifications.
 It is the user's responsibility to ensure that the IC is
 not subjected to over-voltage conditions.
<Ip,1
I.    Rated switch current--SwitcherCAD enters a value from
 the database for the IC it has selected. The LT1070/LT1170
 family current-mode ICs have switch-current ratings that
 decrease linearly for duty cycles above 50%. SwitcherCAD
 recomputes the maximum switch-current rating for the actual
 operating duty cycle to ensure that switch-current ratings
 are not exceeded. If this parameter is increased, SwitcherCAD
 may generate a design that exceeds datasheet limits. Please
 be responsible, folks.
<Rsw,1
I.    Switch on resistance--SwitcherCAD enters a value from
 the database for the IC it has selected, but to give more
 realistic results for efficiency, etc., it uses a value
 which may be slightly less than the worst-case-over-temperature
 specification.
<Vs,1
I.    Switch offset voltage loss--SwitcherCAD enters a value
 from the database for the IC it has selected. This parameter
 is the extrapolated voltage drop across the switch at zero
 switch current. It is zero for IC's in the LT1070 family
 which use saturating switch designs. Emitter-follower switches
 like those used in the LT1074 and LT1076 will have a value
 between 0.5V and 1.5V.
<Fkhz,1
I.    Switching frequency--SwitcherCAD enters a value from
 the database for the IC it has selected. This parameter
 can be altered to check the effects of worst-case variations
 in frequency. Lower frequencies will increase peak device
 current levels, and higher frequencies will increase ac
 switching losses.
<DCmax,1
I.    Maximum duty cycle--SwitcherCAD enters a value from
 the database for the IC it has selected. This parameter
 may limit minimum input voltage.
<Vd,1
I.    Diode forward voltage used for calculations--To keep
 SwitcherCAD equations manageable, diode forward voltage
 is treated as a constant. This is reasonable if the value
 chosen represents the full load condition. At lighter loads,
 efficiency will appear slightly lower, but if this is important,
 a new number can be inserted. If the diode's maximum reverse
 voltage is less than 40V, SwitcherCAD selects a Schottky
 diode with a forward voltage drop of 0.5V. Otherwise, a
 silicon diode is chosen, with a forward voltage drop of
 0.8V.
<CkHz_kGs,1
I.    Core loss constant (C)--This and the next three constants
 are used to describe inductor core material for calculating
 core loss. Appendix E describes how these constants are
 calculated. SwitcherCAD inserts numbers for Type 52 powdered-iron
 material. Be extremely careful when changing these numbers
 because even small errors here can result in large errors
 in calculated core loss.
<d,1
I.    Core loss frequency exponent (d)--See "Core loss constant,"
 above.
<p,1
I.    Core loss flux density exponent (p)--See "Core loss
 constant," above.
<U,1
I.    Core permeability (u)--See "Core loss constant," above.
<PctCuL,1
I.    Enter copper loss (% of Pout)--SwitcherCAD uses this
 number to calculate the maximum inductor series resistance
 needed to achieve the specified power loss at maximum load
 current. This number can be increased to yield smaller inductors
 or decreased for greater efficiency. If peak load current
 is significantly higher than normal load current, but the
 peak is of short duration (<10s), consider using a smaller
 inductor with higher resistance. Be careful to avoid saturation
 at peak load currents. Short-circuit conditions may cause
 destructive overheating in small inductors, so make informed
 decisions in this regard.
<ESRL,1
O.    Inductor Resistance  for copper loss--Calculated based
 on copper loss, see above.
<PctCLsug,1
O.    Suggested core loss--SwitcherCAD selects a core loss
 based upon maximum output power. The suggested core loss
 varies from 5% at 1 watt and below to 2% at 10 watts and
 above. SwitcherCAD computes a minimum value of inductance
 to achieve this loss, using maximum input voltage, where
 core loss is highest, and type 52 powdered iron material.
 See Appendix E for details.
<PctCL,1
I.    Enter desired core loss--If SwitcherCAD's selection
 for core loss (above) is unacceptable, change it here. SwitcherCAD
 uses this value for calculations.
<LminCoreVinH,1
O.    Min inductor needed for core loss--See "Suggested core
 loss," (above).
<C89,1
O.    Min inductor needed for output power--SwitcherCAD computes
 the minimum value needed at full load to ensure that switch-current
 rating is not exceeded. For conservative designs, a 40%
 "fudge factor" has been added to the suggested inductance
 because the inductor's permeability changes with dc current
 levels. Minimum input voltage is used in the calculation
 because that is where peak inductor current is highest.
 The calculated value of inductance will often be tantalizing
 low, but may result in excessive core loss. A practical
 value will normally be somewhat higher to reduce core loss,
 avoid large switch currents, provide guardbands, etc.
<C77,5
O.    Min inductor needed for output power--SwitcherCAD computes
 the minimum value needed at full load to ensure that switch-current
 rating is not exceeded. For conservative designs, a 40%
 "fudge factor" has been added to the suggested inductance
 because the inductor's permeability changes with dc current
 levels. Minimum input voltage is used in the calculation
 because that is where peak inductor current is highest.
 The calculated value of inductance will often be tantalizing
 low, but may result in excessive core loss. A practical
 value will normally be somewhat higher to reduce core loss,
 avoid large switch currents, provide guardbands, etc.
<PLSug,1
O.    Suggested inductor--SwitcherCAD selects the larger
 of the two inductors above to meet both switch-current and
 core-loss requirements.
<PL,1
I.    Enter chosen inductor--SwitcherCAD will initially use
 a value chosen from the database that meets or exceeds both
 the suggested inductance value and the copper loss requirement.
 If the database does not contain an appropriate value, the
 program selects a value of 1,000,000mH. The user may change
 the value at will. SwitcherCAD uses this value for actual
 operating-condition calculations.
<PLRsel,1
I.    Enter inductor series resistance--SwitcherCAD initially
 enters the dc resistance of the inductor chosen above. If
 the program cannot find an appropriate inductor in the database
 (see above), it selects a inductor series resistance of
<C193,1
O.    Operating mode at full load current--"Cont" or "Discont"
 indicates whether the regulator is in continuous or discontinuous
 mode at full load current.
<C194,1
O.    Duty cycle--SwitcherCAD calculates operating conditions,
 including duty cycle, at minimum input voltage. Duty cycles
 above 50% will affect maximum available load current when
 using current-mode switchers, such as the LT1070/LT1170
 family.
0.
<C184,5
O.    Operating mode at full load current--"Cont" or "Discont"
 indicates whether the regulator is in continuous or discontinuous
 mode at full load current.
<DCvar1,5
O.    Duty cycle--SwitcherCAD calculates operating conditions,
 including duty cycle, at minimum input voltage. Duty cycles
 above 50% will affect maximum available load current when
 using current-mode switchers, such as the LT1070/LT1170
 family.
<IswMaxVinL,1
O.    Max rated switch current at this duty cycle--See above.
 Maximum available switch current drops about 0.67% for each
 1% increase in duty cycle above 50% for the LT1070/LT1170
 family regulators.
<ILpkVinL,1
O.    Peak inductor/switch current--This current must be
 lower than the maximum-rated switch-current limit (see above)
 in order to ensure that the IC is being operated within
 specifications.
<Icrit,1
O.    Output current at crossover--SwitcherCAD calculates
 the load current at which the regulator is operating at
 the boundary between continuous and discontinuous modes.
 At high input voltage, the regulator will shift to continuous
 mode at higher load currents. Unless transient response
 is critical, shifting to discontinuous mode does not affect
 the performance of the regulator.
<C198,1
O.    Is max switch current exceeded?--Peak switch current
 is compared to maximum-rated switch current at the operating
 duty cycle (see above) to ensure that the IC is being operated
 within its specifications. If the rated switch-current limit
 is exceeded, a "Yes" is displayed here. If this occurs,
 a larger inductor value or an IC with a higher switch-current
 rating must be used.
<C189,5
O.    Is max switch current exceeded?--Peak switch current
 is compared to maximum-rated switch current at the operating
 duty cycle (see above) to ensure that the IC is being operated
 within its specifications. If the rated switch-current limit
 is exceeded, a "Yes" is displayed here. If this occurs,
 a larger inductor value or an IC with a higher switch-current
 rating must be used.
<MaxDCe,1
O.    Is max duty cycle exceeded?--If the IC's maximum duty
 cycle has been exceeded, a "Yes" is displayed here. LTC
 switchers have a maximum duty cycle of 80%-90% depending
 on the particular part type. Maximum duty cycle limits minimum
 input voltage for the regulator. Refer to Table 3.2.2 for
 the ICs maximum duty cycle rating.
<ILRMSVinL,1
O.    RMS inductor current--The inductor's RMS current is
 usually slightly higher than its average current. The inductor's
 RMS current and its desired copper loss are used to determine
 wire size. Worst-case RMS current occurs at minimum input
 voltage.
<ILpkVinL,1
O.    Peak inductor current--The selected inductor must not
 saturate at this current level.
<ILIppVinL,1
O.    P-P inductor ripple current--Peak-to-peak inductor
 current is determined by switching frequency, input voltage,
 and inductance value. It determines inductor core loss.
 Larger value inductors will improve core loss but will be
 physically larger and more expensive. Worst-case core loss
 occurs at the maximum input voltage.
<C271,1
O.    Inductor V*us product--This is the product of voltage
 across an inductor and the time it is present. This product
 determines inductor ripple current, and therefore core loss.
 Inductor manufacturers often specify maximum volt'microsecond
 (V'ms) product for their inductors to avoid excess heating
 due to core loss. This parameter is specified by the manufacturer
 at a particular frequency and the maximum limit must be
 adjusted for other frequencies.
<ICRMSVinL,1
O.    Input capacitor RMS ripple current--This is an extremely
 important parameter because it determines the physical size
 of the input capacitor. Worst-case RMS capacitor current
 does not necessarily occur at the minimum input voltage.
 The worst-case condition is with the input voltage equal
 to 2'(Vout).
    The RMS current in the input capacitor is much lower
 than that in the output capacitor, because it is filtered
 by the inductor. The input capacitor size is determined
 by ripple current and can be decreased by increasing the
 inductance. See Appendix A for further details.
<ICESRsel,1
I.    Enter input capacitor ESR--This value is used to calculate
 power loss in the input capacitor for efficiency calculations.
 If the database does not contain an appropriate filter capacitor,
 the program selects an ESR of 0.
<ICValsel,1
I.    Enter input capacitor value--The actual value of the
 input capacitor in microfarads is not important, because
 the capacitor is assumed to be purely resistive at switching
 frequencies. SwitcherCAD uses this value simply for the
 parts list printout. If the database does not contain an
 appropriate value, the program selects a value of 1,000,000mF.
<OCRMSVinL,1
O.    Output capacitor RMS ripple current--This is an extremely
 important parameter because it determines the physical size
 of the output capacitor, which may be one of the largest
 components in the regulator. Worst-case operating point
 occurs at the minimum input voltage.
    SwitcherCAD selects multiple capacitors from the database
 if the output capacitor's RMS ripple current exceeds the
 maximum ripple-current rating of the capacitors in the database.
 Paralleling allows sharing of the ripple current between
 capacitors. See Appendix A for further details.
<OCESRmax,1
O.    Output-capacitor ESR for ripple voltage--This is the
 ESR (effective series resistance) needed in the output capacitor
 to meet the ripple voltage specification without requiring
 an additional output filter. For low output ripple specifications,
 the ESR may be unreasonably low and a filter will be needed.
 Keep in mind that electrolytic capacitor ESR is very temperature
 dependent, increasing dramatically at low temperatures.
<OCESRsel,1
I.    Enter output-capacitor ESR--Actual ESR of the chosen
 output capacitor can be entered here. If the database does
 not contain an appropriate value, the program selects an
 ESR of 0.
<OCValsel,1
I.    Enter output capacitor value--The actual value of the
 output capacitor in microfarads is not important, because
 the capacitor is assumed to be purely resistive at switching
 frequencies. SwitcherCAD uses this value simply for the
 parts list printout. If the database does not contain an
 appropriate value, the program selects a value of 1,000,000mF.
 Also, this value will be the sum of all capacitors if SwitcherCAD
 selects multiple capacitors to meet the RMS ripple current
 requirement (See parts list printout).
<VoppVinLvar1,1
O.    Output ripple (p-p) without filter--Ripple voltage
 is calculated using the ESR from above. Calculations are
 done at minimum input voltage, which is the worst-case condition
 for output ripple in this topology. Don't forget that capacitor
 ESR increases significantly at low temperatures.
<OutFilterReq,1
O.    Is an output filter required?--The output-ripple voltage
 limit is compared to the output ripple without a filter
 (see above) and if the output ripple voltage limit is exceeded,
 a "Yes" is displayed here.
<FilterAtt,1
O.    Filter attenuation ratio needed--If an output filter
 is needed, SwitcherCAD divides the unfiltered output ripple
 by the specified output voltage ripple to obtain the required
 attenuation.
<FCCdata,1
O.    Suggested Filter Capacitance from database--SwitcherCAD
selects a filter capacitor using the formula 40uF(IOutMax + 0.5). This
 formula is a rule of thumb used by LTC and represents a compromise
 between capacitor size and regulator transient response.
 The capacitance is used only for calculating the filter's
 resonant frequency.
<FCC,1
I.    Enter Filter Capacitance --SwitcherCAD enters the
selected database capacitor here (see above). This value can be
changed if an alternate capacitor is selected. The
capacitance value is used only for calculating the filter's
 resonant frequency.
<FCESRdata,1
O.    Enter filter capacitor ESR--SwitcherCAD enters the
 chosen capacitor's ESR (see above). For sudden changes in
 load current the ESR of this capacitor allows the output
 voltage to shift. If the output voltage variation is unacceptable,
 then a capacitor with lower ESR should be chosen. Refer
 to the LC output filter section for further details.
<FCESRsel1,1
I.    Enter filter capacitor ESR--SwitcherCAD enters the
selected database capacitor ESR here (see above). This value can be
changed if an alternate capacitor is selected.
<FLmin,1
O.    L needed for output ripple--This is the inductance
 value required to obtain the calculated filter attenuation.
 Rod- or drum-shaped inductors may be substituted for more
 expensive toroids in the LC output filter, because ripple
 current is usually low enough to avoid magnetic-field radiation
 problems.
<FLsel,1
I.    Enter actual L selected--SwitcherCAD selects the smallest
 inductor in the database that has the required inductance
 and is rated to handle full load current.
<C228,1
O.    Output ripple voltage after filter--Actual output ripple
 is calculated using the LC filter capacitor ESR and the
 inductance selected above.
<C230,1
O.    Resonant frequency of filter--This frequency is calculated
 to allow comparison to the frequencies of dynamic loads.
 At the resonant frequency, the filter's output impedance
 is at its maximum.
<C219,5
O.    Output ripple voltage after filter--Actual output ripple
 is calculated using the LC filter capacitor ESR and the
 inductance selected above.
<C221,5
O.    Resonant frequency of filter--This frequency is calculated
 to allow comparison to the frequencies of dynamic loads.
 At the resonant frequency, the filter's output impedance
 is at its maximum.
<IpkVinL,1
O.    Peak switch current--transferred from a previous line
 and displayed here for informational purposes.
<IswAvgVinL,1
O.    Average switch current during on-time--The worst-case
 condition occurs at the minimum input voltage.
<PIC,1
O.    Power dissipated in IC--This is the total power dissipated
 in the IC, including power from quiescent current, switch-on
 voltage, switch rise and fall times, and the switch driver.
 The worst-case condition occurs at the minimum input voltage
 because switch-conduction losses dominate IC dissipation.
<TjICMax,1
O.    Maximum-rated IC junction temperature--Transferred
 from the Design Specification screen.
<ThetaJAIC,1
I.    Thermal resistance of IC JA--Junction-to-ambient thermal
 resistance is transferred from the database. No external
 heatsink is assumed.
<ThetaJCIC,1
I.    Thermal resistance of IC JC--Junction-to-case thermal
 resistance is transferred from the database.
<C243,1
O.    Is an IC heatsink required?--IC junction temperature
 is calculated assuming no external heatsink. If the maximum
 junction temperature is exceeded, a "Yes" is displayed here
 and a heatsink must be added in order to meet the IC's maximum
 junction temperature requirement.
<C234,5
O.    Is an IC heatsink required?--IC junction temperature
 is calculated assuming no external heatsink. If the maximum
 junction temperature is exceeded, a "Yes" is displayed here
 and a heatsink must be added in order to meet the IC's maximum
 junction temperature requirement.
<RICThetaCA,1
O.    Max thermal resistance of IC heatsink--If a heatsink
 is required, SwitcherCAD calculates the heatsink thermal
 resistance using IC power dissipation and junction-to-case
 thermal resistance. This heatsink is the bare minimum required
 for reliable operation, and will result in the IC operating
 at its maximum-rated junction temperature. We strongly recommend
 that a larger heatsink be used if the regulator is expected
 to operate at maximum load current for extended periods.
<ThetaCAICHS,1
I.    Enter thermal resistance of heatsink--The value calculated
 above is initially displayed here, but the user should enter
 the actual value for the selected heatsink.
<TIC,1
O.    IC temperature at max ambient temperature--IC-junction
 temperature is calculated using the actual heatsink thermal
 resistance entered above.
<C249,1
O.    Average diode current--For this topology the average
 diode current is equal to the output current and independent
 of input voltage, but peak diode current (see below) can
 be many times higher.
<C240,5
O.    Average diode current--For this topology the average
 diode current is equal to the output current and independent
 of input voltage, but peak diode current (see below) can
 be many times higher.
<IdpkVinL,1
O.    Peak diode current--Peak diode current is the sum of
 average current during switch on-time and one-half of the
 peak-to-peak inductor ripple current. This is included primarily
 for informational purposes.
<C251,1
O.    Average diode current during on time--In this case,
 "on time" refers to the period when the diode is conducting,
 rather than to switch on-time. Diode current during this
 period can be much higher than load current, so caution
 must be used in selecting the diode. SwitcherCAD selects
 an output diode by adding the average diode current during
 on-time to the output current and then dividing the result
 by two. This was done to accommodate the high pulse currents
 in the output diode. The peak diode current increases as
 the input voltage decreases; it is proportional to the output
 voltage divided by the input voltage multiplied by the output
 current. The worst case condition occurs at the minimum
 input voltage.
<C242,5
O.    Average diode current during on time--In this case,
 "on time" refers to the period when the diode is conducting,
 rather than to switch on-time. Diode current during this
 period can be much higher than load current, so caution
 must be used in selecting the diode. SwitcherCAD selects
 an output diode by adding the average diode current during
 on-time to the output current and then dividing the result
 by two. This was done to accommodate the high pulse currents
 in the output diode. The peak diode current increases as
 the input voltage decreases; it is proportional to the output
 voltage divided by the input voltage multiplied by the output
 current. The worst case condition occurs at the minimum
 input voltage.
<IdVrmaxVinH,1
O.    Max diode reverse voltage @VinH--For this topology
 it is equal to the output voltage.
<C253,1
O.    Suggested diode type--If the diode's maximum reverse
 voltage is less than 40V SwitcherCAD selects a Schottky
 diode with a forward voltage drop of 0.5V. Otherwise, a
 silicon diode is chosen with a forward voltage drop of 0.8V.
<C244,5
O.    Suggested diode type--If the diode's maximum reverse
 voltage is less than 40V SwitcherCAD selects a Schottky
 diode with a forward voltage drop of 0.5V. Otherwise, a
 silicon diode is chosen with a forward voltage drop of 0.8V.
<Vf,1
I.    Diode forward voltage for thermal calc--The forward
 voltage drop of many diodes operating at high current densities
 decreases as ambient temperature is increased, at a rate
 of approximately -1mV/oC. To do a "worst-case" analysis
 of diode's junction temperature, use the actual diode forward
 voltage drop at the maximum operating temperature; otherwise
 the calculated temperature will be artificially high. Enter
 a number here which represents the diode's high temperature
 forward voltage at a current equal to the average diode
 current during on-time.
    SwitcherCAD indicates that diode dissipation is independent
 of input voltage, because the program assumes a fixed value
 for the diode forward voltage and because average diode
 current is always equal to output current. Actually, diode
 dissipation will be somewhat lower at maximum input voltage,
 because peak diode current is lower and therefore Vf is
 lower. Refer to Appendix D for further details.
<Trr,1
I.    Diode reverse recovery time--If a Schottky diode is
 chosen, the recovery time is assumed to be zero. Otherwise,
 for a silicon diode, SwitcherCAD enters the value from its
 database for the chosen diode.
<Pdiod,1
O.    Power dissipated in diode--This is the sum of forward
 losses and reverse-recovery losses. SwitcherCAD assumes
 that all reverse-recovery loses are dissipated in the diode,
 whereas in actual operation, some of the losses may be transferred
 to the IC. In SwitcherCAD, Schottky diode power dissipation
 is independent of input voltage, because it is equal to
 the assumed diode forward voltage drop multiplied by the
 output current. In an actual circuit, however, the worst-case
 diode dissipation occurs at the minimum input voltage, where
 the diode forward voltage drop is highest.
<TjDMax,1
O.    Max rated diode junction temperature--Transferred from
 the Design Specification screen.
<ThetaJAD,1
I.    Thermal resistance of diode JA--This number is transferred
 from the database and assumes no heatsink. Enter the appropriate
 figure if the diode type is changed.
<ThetaJCD,1
I.    Thermal resistance of diode JC--This number is transferred
 from the database. Enter the appropriate figure if the diode
 type is changed.
<C262,1
O.    Is a diode heatsink required?--Diode junction temperature
 is calculated assuming no external heatsink. If the maximum
 junction temperature is exceeded, a "Yes" is displayed here
 and a heatsink must be added in order to meet the diode's
 maximum junction temperature requirement. Diode thermal
 resistance is critically dependent on mounting technique,
 especially for axial-lead diodes. Some manufacturers unrealistically
 assume ideal mounting conditions when specifying diode thermal
 resistance. Always consult the diode data sheet carefully
 before committing to a diode type and/or mounting procedure.
<RDThetaCA,1
O.    Maximum thermal resistance of diode heatsink--If a
 heatsink is required SwitcherCAD enters the maximum thermal
 resistance based on maximum ambient temperature and junction-to-case
 thermal resistance.
<ThetaCADHS,1
I.    Enter thermal resistance of diode heatsink--The value
 calculated above is initially displayed here, but the user
 should enter the actual value for the selected heatsink.
<TD,1
O.    Diode temperature at maximum ambient temperature--The
 diode temperature is calculated at minimum input voltage,
 using the actual value for the heatsink entered in the previous
 line.
<Dummy4,7
5.4 Tapped-Inductor

<vout,7
I.    Main Output Voltage--This value is transferred from
 the Design Specification screen, but you can change it here
 if you wish.
<vinmin,7
I.    Minimum input voltage--This value is transferred from
 the Design Specification screen. You should definitely change
 the minimum input voltage as part of the design procedure,
 because SwitcherCAD calculates detailed operating conditions
 only at minimum input voltage. This was done because, for
 many topologies, minimum input voltage represents a worst-case
 current condition for most of the components. In a tapped-inductor
 converter, switch dissipation is highest at low VIN, but
 diode and inductor dissipation are highest at high VIN,
 and input and output capacitor dissipation are highest at
 VIN = 2'(VOUT). To "worst case" a tapped-inductor design,
 you must check operating conditions with the minimum input
 voltage equal to 2'(VOUT) and equal to maximum input voltage.
 Ac losses in the switch are highest at the maximum input
 voltage, and can become significant. Refer to Table 5.4.1
 for worst-case operating conditions for each power component.

<vinnom,7
I.    Nominal input voltage--This input was originally included
 in SwitcherCAD as a condition for calculating efficiency.
 It was dropped from use when the program and run time became
 too long, but remains available for future use.
<vinmax,7
I.    Maximum input voltage--Maximum input voltage is used
 only to calculate worst-case voltage conditions for the
 IC, catch diode, and input capacitor.
<ioutmin,7
I.    Minimum load current--This parameter is not used in
 the tapped-inductor converter program. All tapped-inductor
 designs supported by SwitcherCAD operate down to zero load
 current. They will begin to operate in discontinuous mode
 when load current drops low enough, and SwitcherCAD calculates
 this point for reference.
<ioutnom,7
I.    Nominal load current--Not used. See "Nominal input
 voltage."
<ioutmax,7
I.    Maximum load current--SwitcherCAD calculates operating
 conditions at maximum load current only, so this parameter
 can be modified to observe the effects of load changes on
 various parameters.
<DVopp,7
I.    Output-ripple voltage--Ripple voltage is specified
 by the user, and SwitcherCAD tries to create a design which
 meets this specification without using an additional output
 filter. However, If SwitcherCAD decides that the output
 capacitor would be unreasonably large, it adds an output
 filter and computes values to meet the ripple specification.

<tamax,7
I.    Max ambient temperature--This parameter is used to
 calculate the amount of heatsinking required for the IC,
 catch diode, and filter capacitors. Remember that SwitcherCAD
 calculates the minimum amount of heatsinking required to
 keep junction temperature below maximum specification. Conservative
 design suggests some guardbanding here.
    When selecting filter capacitors, SwitcherCAD assumes
 maximum ambient temperature and a 20,000 hour required lifetime.
 If SwitcherCAD cannot find a filter capacitor in its database
 to satisfy the lifetime requirement, it will default to
 a 1,000,000mF capacitor. The database contains aluminum
 electrolytic capacitors rated at 105°C. If SwitcherCAD does
 not find a suitable capacitor, then you should select an
 alternate capacitor technology (e.g., Sanyo OS-CON's), use
 paralleled units, or lower the lifetime requirement and
 use the equation in Appendix A to determine the proper filter
 capacitor.
<VswM,7
I.    Maximum-rated switch voltage--SwitcherCAD displays
 a value from the database for the IC it has selected. This
 can be altered for special purposes, but if it is increased
 the resulting design may violate LTC's data-sheet specifications.
 It is the user's responsibility to ensure that the IC is
 not subjected to over-voltage conditions.
<Ip,7
I.    Rated switch current--SwitcherCAD enters a value from
 the database for the IC it has selected. If this parameter
 is increased, SwitcherCAD may generate a design that exceeds
 data-sheet limits. Please be responsible, folks.
<Rsw,7
I.    Switch on resistance--SwitcherCAD enters a value from
 the database for the IC it has selected, but to give more
 realistic results for efficiency, etc., it uses a value
 which may be slightly less than worst-case-over-temperature.

<Vs,7
I.    Switch offset voltage loss--SwitcherCAD enters a value
 from the database for the IC it has selected. This parameter
 is the extrapolated voltage drop across the switch at zero
 switch current. Emitter-follower switches like those used
 in the LT1074 and LT1076 will have a value of 0.5V to 1.5V.

<Fkhz,7
I.    Switching frequency--SwitcherCAD enters a value from
 the database for the IC it has selected. This parameter
 can be altered to check the effects of worst-case variations
 in frequency. Lower frequencies will increase peak device
 current levels, and higher frequencies will increase ac
 switching losses.
<DCmax,7
I.    Maximum duty cycle--SwitcherCAD enters a value from
 the database for the IC it has selected. This parameter
 may limit minimum input voltage.
<Nsug,7
O.    Suggested Turns Ratio--SwitcherCAD defaults to a Coiltronics
 CTX 110398-1, which is optimized for a 5V, 10A output and
 has a turns ratio of 3.
<N,7
I.    Selected Turns Ratio--SwitcherCAD initially displays
 the suggested turns ratio. The turns ratio can be changed,
 but this must be done with caution. If a lower turns ratio
 is used, the duty cycle decreases and the peak switch current
 increases. This could result in a peak switch current in
 excess of the selected device's rated switch-current limit.
 Conversely, a higher turns ratio will increase both the
 duty cycle and the flyback voltage. A catastrophic failure
 may occur if the flyback voltage exceeds the maximum switch
 voltage.
<Vd,7
I.    Diode forward voltage used in calc--To keep SwitcherCAD
 equations manageable, diode forward voltage is treated as
 a constant. This is reasonable if the value chosen represents
 the full-load condition. At lighter loads, efficiency will
 appear slightly lower, but if this is important, a new number
 can be inserted. SwitcherCAD selects a Schottky diode with
 a forward voltage drop of 0.5V.
<a,7
I.    Core loss constant (a)--This and the next three constants
 are used to describe inductor core material for calculating
 core loss. Appendix E describes how these constants are
 calculated. SwitcherCAD inserts numbers for Type 52 powdered-iron
 material. Be extremely careful when changing these numbers
 because even small errors here can result in large errors
 in calculated core loss.
<d,7
I.    Core loss frequency exponent (d)--See "Core loss constant,"
 above.
<p,7
I.    Core loss flux density exponent (p)--See "Core loss
 constant," above.
<U,7
I.    Core permeability (u)--See "Core loss constant," above.
<Rpri,7
O.    Suggested primary resistance--SwitcherCAD defaults
 to 0.03 ohms.
<Rsec,7
O.    Suggested secondary resistance--SwitcherCAD defaults
 to 0.01 ohms.
<PLSug,7
O.    Suggested Inductance--SwitcherCAD defaults to 100mH.
<PL,7
I.    Enter chosen inductor--See "Suggested inductance,"
 above.
<PctLeakL,7
I.    Enter leakage inductance loss--SwitcherCAD defaults
 to 1.0%.
<Leakvar1,7
O.    Leakage inductance--Calculated from above. As leakage
 inductance increases so does the power dissipation in the
 snubber zener. Leakage inductance can be minimized by bifilar
 winding the primary with the secondary.
<Rprisel,7
I.    Enter primary series resistance--See "Suggested primary
 resistance," above.
<Rsecsel,7
I.    Enter Secondary Series Resistance--See "Suggested secondary
 resistance," above.
<C155,7
O.    Operating mode at full load current--"Cont" or "Discont"
 indicates whether the regulator is in continuous or discontinuous
 mode at full load current.
<C156,7
O.    Duty cycle--SwitcherCAD calculates operating conditions,
 including duty cycle, at minimum input voltage.
<IswMaxVinL,7
O.    Max rated switch current at this duty cycle--See above.

<IswIpkVinL,7
O.    Peak inductor/switch current--This current must be
 lower than the maximum-rated switch-current limit (see above)
 in order to ensure that the IC is being operated within
 specifications.
<Icrit,7
O.    Output current at crossover--SwitcherCAD calculates
 the load current at which the regulator is operating at
 the boundary between continuous and discontinuous modes.
 At high input voltage, the regulator will shift to continuous
 mode at higher load currents. Unless transient response
 is critical, shifting to discontinuous mode does not affect
 the performance of the regulator.
<C160,7
O.    Is max switch current exceeded?--Peak switch current
 is compared to maximum-rated switch current at the operating
 duty cycle (see above) to ensure that the IC is being operated
 within its specifications. If the rated switch-current limit
 is exceeded, a "Yes" is displayed here. If this occurs,
 a larger inductor value or an IC with a higher switch current
 rating must be used.
<MaxDCe,7
O.    Is max duty cycle exceeded?--If the IC's maximum duty
 cycle has been exceed, a "Yes" is displayed here. This limits
 minimum input voltage for the regulator; refer to Table
 3.2.2.
<ILRMSVinL,7
O.    RMS inductor current in "1" winding-- The inductor's
 RMS current and its desired copper loss are used to determine
 its wire size. Worst-case RMS current occurs at minimum
 input voltage.
O.    RMS inductor current in "N" winding-- The inductor's
 RMS current and its desired copper loss are used to determine
 its wire size. Worst-case RMS current occurs at minimum
 input voltage.
<ILpkVinL,7
O.    Peak inductor current--The selected inductor must not
 saturate at this current level.
<ILIppVinL,7
O.    P-P inductor ripple current--Peak-to-peak inductor
 current is determined by switching frequency, input voltage,
 and inductance value. It determines inductor core loss.
 Larger value inductors will improve core loss but will be
 physically larger and more expensive. Worst-case operating
 condition occurs at the maximum input voltage.
<C235,7
O.    Inductor V*ms product--This is the product of voltage
 across an inductor and the time it is present. This product
 determines inductor ripple current, and therefore core loss.
 Inductor manufacturers often specify maximum volt'microsecond
 (V*ms) product for their inductors to avoid excess heating
 due to core loss. This parameter is specified by the manufacturer
 at a particular frequency and the maximum limit must be
 adjusted for other frequencies.
<ICRMSVinL,7
O.    Input capacitor RMS ripple current--This is an extremely
 important parameter because it determines the physical size
 of the input capacitor, which may be one of the largest
 components in the regulator. Worst-case capacitor current
 occurs at the minimum input voltage.
    SwitcherCAD will select multiple capacitors from the
 database if the input capacitor's RMS ripple current exceeds
 the maximum ripple-current rating of the capacitors in the
 database. Paralleling allows sharing of the ripple current
 between capacitors. See Appendix A for further details.
<ICESRsel,7
I.    Enter input capacitor ESR--This value is used to calculate
 power loss in the input capacitor for efficiency calculations.
 If the database does not contain an appropriate filter capacitor,
 the program selects an ESR of 0.
<ICValsel,7
I.    Enter input capacitor value--The actual value of the
 input capacitor in microfarads is not important, because
 the capacitor is assumed to be purely resistive at switching
 frequencies. SwitcherCAD uses this value simply for the
 parts list printout. If the database does not contain an
 appropriate value, the program selects a value of 1,000,000mF.
<OCRMSVinL,7
O.    Output capacitor RMS ripple current--This is an extremely
 important parameter because it determines the physical size
 of the output capacitor, which may be one of the largest
 components in the regulator. Worst-case capacitor current
 occurs at the minimum input voltage.
    SwitcherCAD will select multiple capacitors from the
 database if the input capacitor's RMS ripple current exceeds
 the maximum ripple-current rating of the capacitors in the
 database. Paralleling allows sharing of the ripple current
 between capacitors. See Appendix A for further details.
<OCESRmax,7
O.    Output-capacitor ESR for ripple voltage--This is the
 ESR (effective series resistance) needed in the output capacitor
 to meet the ripple voltage specification without requiring
 an additional output filter. For low output-ripple specifications,
 the ESR may be unreasonably low and a filter will be needed.
 Keep in mind that electrolytic capacitor ESR is very temperature
 dependent, increasing dramatically at low temperatures.
<OCESRsel,7
I.    Enter output-capacitor ESR--Actual ESR of the chosen
 output capacitor can be entered here. If the database does
 not contain an appropriate value, the program selects an
 ESR of 0.
<OCValsel,7
I.    Enter output capacitor value--The actual value of the
 output capacitor in microfarads is not important, because
 the capacitor is assumed to be purely resistive at switching
 frequencies. SwitcherCAD uses this value simply for the
 parts list printout. If the database does not contain an
 appropriate value, the program selects a value of 1,000,000mF.
 Also, this value will be the sum of all capacitors if SwitcherCAD
 selects multiple capacitors to meet the RMS ripple current
 requirement (See parts list printout).
<VoppVinLvar1,7
O.    Output ripple (P-P) without filter--Ripple voltage
 is calculated using the ESR from above. Calculations are
 done at minimum input voltage, which is the worst-case condition
 for output ripple in this topology. Don't forget that capacitor
 ESR increases significantly at low temperatures.
<OutFilterReq,7
O.    Is an output filter required?--The output-ripple voltage
 limit is compared to the output ripple without a filter
 (see above) and if the output-ripple voltage limit is exceeded,
 a "Yes" is displayed here.
<FilterAtt,7
O.    Filter attenuation ratio needed--If an output filter
 is needed, SwitcherCAD divides the unfiltered output ripple
 by the specified output voltage ripple to obtain the required
 attenuation.
<FCCdata,7
O.    Suggested Filter Capacitance from database--SwitcherCAD
selects a filter capacitor using the formula 40uF(IOutMax + 0.5). This
 formula is a rule of thumb used by LTC and represents a compromise
 between capacitor size and regulator transient response.
 The capacitance is used only for calculating the filter's
 resonant frequency.
<FCC,7
I.    Enter Filter Capacitance --SwitcherCAD enters the
selected database capacitor here (see above). This value can be
changed if an alternate capacitor is selected. The
capacitance value is used only for calculating the filter's
 resonant frequency.
<FCESRdata,7
O.    Enter filter capacitor ESR--SwitcherCAD enters the
 chosen capacitor's ESR (see above). For sudden changes in
 load current the ESR of this capacitor allows the output
 voltage to shift. If the output voltage variation is unacceptable,
 then a capacitor with lower ESR should be chosen. Refer
 to the LC output filter section for further details.
<FCESRsel1,7
I.    Enter filter capacitor ESR--SwitcherCAD enters the
selected database capacitor ESR here (see above). This value can be
changed if an alternate capacitor is selected.
<FLmin,7
O.    L needed for output ripple--This is the inductance
 value required to obtain the calculated filter attenuation.
 Rod- or drum-shaped inductors may be substituted for more
 expensive toroids in the LC output filter, because ripple
 current is usually low enough to avoid magnetic-field radiation
 problems.
<FLsel,7
I.    Enter actual L selected--SwitcherCAD selects the smallest
 inductor in the database that has the required inductance
 and is rated to handle full load current.
<C190,7
O.    Output ripple voltage after filter--Actual output ripple
 is calculated using the LC filter capacitor ESR and the
 inductance selected above.
<C192,7
O.    Resonant frequency of filter--This frequency is calculated
 to allow comparison to the frequencies of dynamic loads.
 At the resonant frequency, the filter's output impedance
 is at its maximum.
<IpkVinL,7
O.    Peak switch current--transferred from a previous line
 and displayed here for informational purposes.
<IswAvgVinL,7
O.    Average switch current during on-time--The worst-case
 condition occurs at the minimum input voltage.
<PIC,7
O.    Power dissipated in IC--This is the total power dissipated
 in the IC, including power from quiescent current, switch-on
 voltage, switch rise and fall times, and the switch driver.
 The worst-case condition occurs at the minimum input voltage,
 because switch-conduction losses dominate IC dissipation.
 At higher input voltages the ac loss can become significant.
<TjICMax,7
O.    Maximum-rated IC junction temperature--Transferred
 from the Design Specification screen.
<ThetaJAIC,7
I.    Thermal resistance of IC JA--Junction-to-ambient thermal
 resistance is transferred from the database. No external
 heatsink is assumed.
<ThetaJCIC,7
I.    Thermal resistance of IC JC--Junction-to-case thermal
 resistance is transferred from the database.
<C206,7
O.    Is an IC heatsink required?--IC junction temperature
 is calculated assuming no external heatsink. If the maximum
 junction temperature is exceeded, a "Yes" is displayed here
 and a heatsink must be added in order to meet the IC's maximum
 junction-temperature requirement.
<RICThetaCA,7
O.    Max thermal resistance of IC heatsink--If a heatsink
 is required, SwitcherCAD calculates the heatsink thermal
 resistance using IC power dissipation and junction-to-case
 thermal resistance. This heatsink is the bare minimum required
 for reliable operation, and will result in the IC operating
 at its maximum-rated junction temperature. We strongly recommend
 that a larger heatsink be used if the regulator is expected
 to operate at maximum load current for extended periods.
<ThetaCAICHS,7
I.    Enter thermal resistance of heatsink--The value calculated
 above is initially displayed here, but the user should enter
 the actual value for the selected heatsink.
<TIC,7
O.    IC temperature at max ambient temperature--IC-junction
 temperature is calculated using the actual heatsink thermal
 resistance entered above.
<IdAvgVinL,7
O.    Average diode current--For this topology the average
 diode current is less than the output current. This current
 is at its maximum at high input voltage, not at minimum
 input voltage, where SwitcherCAD calculates operating conditions.
 The user should increase minimum input voltage to the maximum
 figure to check worst-case diode current. SwitcherCAD selects
 the minimum current rating of the diode by multiplying output
 current by 1.5.
<IdpkVinL,7
O.    Peak diode current--Peak diode current is the sum of
 average current during switch on-time and one-half of the
 peak-to-peak inductor ripple current. This is included primarily
 for informational purposes.
<IdAvgOnVinL,7
O.    Average diode current during on time--In this case,
 "on time" refers to the period when the diode is conducting,
 rather than to switch on-time. The worst case condition
 occurs at the maximum input voltage.
<IdVrmaxVinH,7
O.    Max diode reverse voltage @VinH--For this topology
 it is 0.25 times the difference between the input and output
 voltages plus the output voltage.
<C218,7
O.    Suggested diode type--SwitcherCAD selects a Schottky
 diode with a forward voltage drop of 0.5V.
<Vf,7
I.    Diode forward voltage for thermal calc--The forward
 voltage drop of many diodes operating at high current densities
 decreases as ambient temperature is increased, at a rate
 of approximately -1mV/oC. To do a worst-case analysis of
 diode's junction temperature, use the actual diode forward
 voltage drop at the maximum operating temperature; otherwise
 the calculated temperature will be artificially high. Enter
 a number here which represents the diode's high-temperature
 forward voltage at a current equal to the average diode
 current during on-time. Refer to Appendix D for further
 details.
<Trr,7
I.    Diode reverse recovery time--If a Schottky diode is
 chosen, the recovery time is assumed to be zero.
<Pdiod,7
O.    Power dissipated in diode--This is the sum of forward
 losses and reverse-recovery losses. SwitcherCAD assumes
 that all reverse-recovery loses are dissipated in the diode,
 whereas in actual operation, some of the losses may be transferred
 to the IC. The worst-case diode dissipation occurs at the
 maximum input voltage.
<TjDMax,7
O.    Max rated diode junction temperature--Transferred from
 the Design Specification screen.
<ThetaJAD,7
I.    Thermal resistance of diode JA--This number is transferred
 from the database and assumes no heatsink. Enter the appropriate
 figure if the diode type is changed.
<ThetaJCD,7
I.    Thermal resistance of diode JC--This number is transferred
 from the database. Enter the appropriate figure if the diode
 type is changed.
<C226,7
O.    Is a diode heatsink required?--Diode junction temperature
 is calculated assuming no external heatsink. If the maximum
 junction temperature is exceeded, a "Yes" is displayed here
 and a heatsink must be added in order to meet the diode's
 maximum junction-temperature requirement. Diode thermal
 resistance is critically dependent on mounting technique,
 especially for axial-lead diodes. Some manufacturers unrealistically
 assume ideal mounting conditions when specifying diode thermal
 resistance. Always consult the diode data sheet carefully
 before committing to a diode type and/or mounting procedure.
<RDThetaCA,7
O.    Maximum thermal resistance of diode heatsink--If a
 heatsink is required SwitcherCAD enters the maximum thermal
 resistance based on maximum ambient temperature and junction-to-case
 thermal resistance
<ThetaCADHS,7
I.    Enter thermal resistance of diode heatsink--The value
 calculated above is initially displayed here, but the user
 should enter the actual value for the selected heatsink.
<TD,7
O.    Diode temperature at maximum ambient temperature--Diode
 temperature is calculated at minimum input voltage, using
 the actual value for the heatsink entered in the previous
 line.
<Vzmax,7
O.    Max zener volts for clipping (5V guardband)--SwitcherCAD
 computes this by subtracting 5V from the maximum switch
 voltage with respect to ground-pin rating. SwitcherCAD will
 decrease the zener voltage if the switch voltage with respect
 to the input voltage rating has been exceeded.
<Vzmin,7
O.    Minimum zener voltage (Vsnub = 5V)--SwitcherCAD computes
 this by adding 5V to the flyback voltage (N'(Vout + 0.5)).
<VzSug,7
O.    Suggested zener voltage--SwitcherCAD takes the average
 of the previous two voltages.
<Vz,7
I.    Selected zener voltage--SwitcherCAD inserts the suggested
 zener voltage. The user can enter a new value, but caution
 must be used. Higher values reduce zener dissipation, but
 risk switch over-voltage. Lower values protect the switch
 better, but may result in excessive zener dissipation. The
 final circuit checkout should include a test of zener current
 waveform to verify zener dissipation.
<PSnub,7
O.    Zener power loss--SwitcherCAD computes the zener power
 loss based on zener voltage, peak switch current, and leakage
 inductance. Worst-case operating condition occurs at the
 minimum input voltage. Zener loss can become significant
 with large primary leakage inductance or low clipper voltage.
<MaxSWvar1,7
O.    Is max switch voltage with respect to ground-pin limit
 exceeded?--A "Yes" is displayed if the selected zener voltage
  exceeds the maximum switch voltage with respect to ground-pin
 limit.
<MaxSWvar2,7
O.    Is max switch voltage with respect to input voltage
 exceeded?--A "Yes" is displayed if the maximum input voltage
 plus the selected zener voltage exceeds the maximum-rated
 switch voltage.
<Dummy5,3
5.5 Flyback (Flyback and Isolated Flyback)

<vout,3
I.    Main Output Voltage--This value is transferred from
 the Design Specification screen, but you can change it here
 if you wish.
<vinmin,3
I.    Minimum input voltage--This value is transferred from
 the Design Specification screen. You should definitely change
 the minimum input voltage as part of the design procedure,
 because SwitcherCAD calculates detailed operating conditions
 only at minimum input voltage. This was done because, for
 many topologies, minimum input voltage represents a worst-case
 current condition for most of the components. In a flyback
 converter, switch, diode, transformer, and input and output
 filter capacitor dissipation are highest at low VIN. Ac
 losses in the IC switch and diode are highest at the maximum
 input voltage, and these generally do not become significant.
 Refer to Table 5.5.1 for worst-case operating conditions
 for each power component.
<vinnom,3
I.    Nominal input voltage--This input was originally included
 in SwitcherCAD as a condition for calculating efficiency.
 It was dropped from use when the program run time became
 too long, but remains available for future use.
<vinmax,3
I.    Maximum input voltage--Maximum input voltage is used
 only to calculate worst-case voltage conditions for the
 IC, catch diode, and input capacitor.
<ioutmin,3
I.    Minimum load current--This parameter is not used in
 the flyback converter program. All standard flyback designs
 supported by SwitcherCAD operate down to zero load current.
 They will begin to operate in discontinuous mode when load
 current drops low enough, and SwitcherCAD calculates this
 point for reference. Isolated flyback designs are the exception;
 the output must be high enough to keep isolated flyback
 regulators in continuous mode.
<ioutnom,3
I.    Nominal load current--Not used. See "Nominal input
 voltage."
<ioutmax,3
I.    Maximum load current--SwitcherCAD calculates operating
 conditions at maximum load current only, so this parameter
 can be modified to observe the effects of load changes on
 various parameters.
<DVopp,3
I.    Output-ripple voltage--Ripple voltage is specified
 by the user, and SwitcherCAD tries to create a design which
 meets this specification without using an additional output
 filter. However, If SwitcherCAD decides that the output
 capacitor would be unreasonably large, it adds an output
 filter and computes values to meet the ripple specification.
 The user should carefully examine the resulting design to
 see if human intelligence judicially applied can shift inductor,
 capacitor, and frequency values to meet the ripple specification
 more effectively or economically. Many times, a low ripple
 voltage is rather arbitrarily chosen, and a little hard-nosed
 investigation will show that the load will actually tolerate
 more ripple. If this eliminates the need for the additional
 filter, everyone wins.
<vaux2,3
I.    Output #2 VOUT--See "Output voltage".
<ianom2,3
I.    Output #2 Iout_min--See "Minimum load current".
<iamax2,3
I.    Output #2 Iout_max--See "Maximum load current"
<DVopp2,3
I.    Output #2 ripple voltage--See "Output-ripple voltage"
<vaux3,3
I.    Output #3 VOUT--See "Output voltage"
<ianom3,3
I.    Output #3 Iout_min--See "Minimum load current"
<iamax3,3
I.    Output #3 Iout_max--See "Maximum load current"
<DVopp3,3
I.    Output #3 ripple voltage--See "Output-ripple voltage"
<tamax,3
I.    Max ambient temperature--This parameter is used to
 calculate the amount of heatsinking required for the IC,
 catch diode, and filter capacitors. Remember that SwitcherCAD
 calculates the minimum amount of heatsinking required to
 keep junction temperature below maximum specification. Conservative
 design suggests some guardbanding here.
    When selecting filter capacitors, SwitcherCAD assumes
 maximum ambient temperature and a 20,000 hour required lifetime.
 If SwitcherCAD cannot find a filter capacitor in its database
 to satisfy the lifetime requirement, it will default to
 a 1,000,000mF capacitor. The database contains aluminum
 electrolytic capacitors rated at 105°C. If SwitcherCAD does
 not find a suitable capacitor, then you should select an
 alternate capacitor technology (e.g., Sanyo OS-CON's), use
 paralleled units, or lower the lifetime requirement and
 use the equation in Appendix A to determine the proper filter
 capacitor.
<VswM,3
I.    Maximum-rated switch voltage--SwitcherCAD enters a
 value from the database for the IC it has selected. This
 can be altered for special purposes, but if it is increased
 the resulting design may violate LTC's data-sheet specifications.
 It is the user's responsibility to ensure that the IC is
 not subjected to over-voltage conditions.
<Ip,3
I.    Rated switch current--SwitcherCAD enters a value from
 the database for the IC it has selected. The LT1070/LT1170
 family current-mode ICs have switch-current ratings that
 decrease linearly for duty cycles above 50%. SwitcherCAD
 recomputes the maximum switch-current rating for the actual
 operating duty cycle to ensure that switch-current ratings
 are not exceeded. If this parameter is increased, SwitcherCAD
 may generate a design that exceeds data-sheet limits. Please
 be responsible, folks.
<Rsw,3
I.    Switch on resistance--SwitcherCAD enters a value from
 the database for the IC it has selected, but to give more
 realistic results for efficiency, etc., it uses a value
 which may be slightly less than the worst-case-over-temperature
 specification.
<Vs,3
I.    Switch offset voltage loss--SwitcherCAD enters a value
 from the database for the IC it has selected. This parameter
 is the extrapolated voltage drop across the switch at zero
 switch current. It is zero for ICs in the LT1070 family,
 which use saturating switch designs. Emitter-follower switches
 like those used in the LT1074 and LT1076 will have a value
 between 0.5V and 1.5V.
<Fkhz,3
I.    Switching frequency--SwitcherCAD enters a value from
 the database for the IC it has selected. This parameter
 can be altered to check the effects of worst-case variations
 in frequency. Lower frequencies will increase peak device
 current levels, and higher frequencies will increase ac
 switching losses.
<DCmax,3
I.    Maximum duty cycle--SwitcherCAD enters a value from
 the database for the IC it has selected. This parameter
 may limit minimum input voltage.
<Vd1,3
I.    Diode #1 forward voltage--To keep SwitcherCAD equations
 manageable, diode forward voltage is treated as a constant.
 This is reasonable if the value chosen represents the full-load
 condition. At lighter loads, efficiency will appear slightly
 lower, but if this is important, a new number can be inserted.
 If the diode's maximum reverse voltage is less than 40V
 SwitcherCAD selects a Schottky diode with a forward voltage
 drop of 0.5V. Otherwise, a silicon diode is chosen, with
 a forward voltage drop of 0.8V.
<Vd2,3
I.    Diode #2 forward voltage--See  "Diode #1 forward voltage"
<Vd3,3
I.    Diode #3 forward voltage--See "Diode #1 forward voltage"
<IomEqu,3
O.    Equivalent output current--To simplify equations, SwitcherCAD
 sums the output power for all outputs and divides the sum
 by the main output voltage to compute an equivalent output
 current for the main output. SwitcherCAD calculates all
 operating conditions except the individual output capacitor
 ripples currents based on equivalent output current.
<Pout,3
O.    Total output power--The product of the equivalent output
 current and the main output voltage.
<NMin,3
O.    Minimum transformer turns Ratio--SwitcherCAD selects
 a turns ratio that will not exceed the IC's maximum duty
 cycle, maximum switch voltage, or maximum switch current.
 A low turns ratio allows higher output current because of
 current gain in the transformer but increases switch voltage
 and duty cycle. A high turns ratio reduces voltage stress
 on the IC switch but increases switch current. SwitcherCAD
 calculates two "drop dead" minimum turns ratios; one is
 based on duty cycle and the other, on switch breakdown.
 The program displays the higher of these two values as the
 minimum turns ratio.
<NMax,3
O.    Maximum turns ratio--SwitcherCAD calculates a maximum
 turns ratio based on maximum switch current, assuming the
 device is in continuous mode, with ripple current equal
 to 33% of rated switch current.
<Ns,3
O.    Suggested transformer turns ratio--SwitcherCAD calculates
 a suggested turns ratio by selecting a switch operating
 voltage that is 20V below breakdown for input voltages above
 15V and 30V below breakdown for input voltages of 15V or
 less. This value is very much a compromise. Use it only
 as a guide.
<N,3
I.    Enter turns ratio--(N_Sec/N_Pri)--SwitcherCAD enters
 the suggested transformer turns ratio. This parameter can
 be changed but caution must be used. If a higher transformer
 turns ratio is used, peak switch current increases. This
 could result in a peak switch current in excess of the selected
 device's rated switch-current limit. Conversely, a lower
 transformer turns ratio will increase both the duty cycle
 and the flyback voltage. Rounding the turns ratio to an
 integer ratio such as 1:1, 2:1, 2:3, or the like may make
 the transformer easier to wind and hence cheaper, especially
 for bifiliar windings.
<Vd,3
I.    Diode forward voltage use in calc--If the diode's maximum
 reverse voltage is less than 40V, SwitcherCAD selects a
 Schottky diode with a forward voltage drop of 0.5V. Otherwise,
 a silicon diode is chosen with a forward voltage drop of
 0.8V. SwitcherCAD calculates operating conditions based
 on this forward voltage drop.
<PctCuLTran,3
I.    Enter transformer Cu loss (% of Pout)--SwitcherCAD
 uses this number to calculate the transformer's primary
 and secondary series resistances needed to achieve the specified
 power loss at maximum load current. This number can be increased
 to yield smaller transformers or decreased for greater efficiency.
 SwitcherCAD divides the power loss equally between the primary
 and secondary. If peak load current is significantly higher
 than normal load current, but the peak is of short duration
 (<10s), consider using a smaller transformer with higher
 resistance, but be careful to avoid saturation at peak load
 currents. SwitcherCAD computes transformer loss based only
 on copper loss because it assumes that core loss when ferrite
 materials are used at frequencies of 100kHz and under.
<Rpri,3
I.    Max Primary Series Resistance for Cu Loss--Initial calculation
 based on % copper loss and RMS primary switch current.
<Rsec1,3
I.    Max Secondary #1 Resistance for Cu Loss--Initial calculation
 based on % copper loss and RMS secondary #1 current.
<Rsec2,3
I.    Max Secondary #2 Resistance for Cu Loss--Initial calculation
 based on % copper loss and RMS secondary #2 current.
<Rsec3,3
I.    Max Secondary #3 Resistance for Cu Loss--Initial calculation
 based on % copper loss and RMS secondary #3 current.
<LminPwr,3
O.    Min primary inductance for output power--SwitcherCAD
 computes the minimum primary inductance needed at full load
 to ensure that switch-current rating is not exceeded. For
 conservative designs, several "fudge factors" have been
 added to the calculated inductance to avoid excessive core
 or switch loss and because of production tolerances in the
 transformer. Minimum input voltage is used in the calculation
 because that is where peak primary current is highest. No
 assumption is made about the operating mode; if discontinuous
 mode will supply sufficient operating power, it will be
 selected. The calculated value of primary inductance will
 sometimes be tantalizing low, but may result in excessive
 core or switch loss. A practical value may be somewhat higher
 to reduce core loss, avoid large switch currents, provide
 guardbands, etc.
<LripVinL,3
O.    Primary inductance for 33% ripple current--SwitcherCAD
 determines a primary inductance where the magnetizing current
 (ripple current) is 33% of the rated switch current. This
 is for informational purposes only and corresponds to the
 original calculation preformed by SwitcherCAD to select
 an IC.
<PLSug,3
O.    Suggested primary inductance--SwitcherCAD selects the
 larger of either the minimum inductance for output power
 or 25mH. 25mH was chosen as a lower limit to prevent excessive
 di/dt in the IC switch at high input voltage.
<PL,3
I.    Enter chosen primary inductance--Initially, SwitcherCAD
 enters the suggested primary inductance from above. A database
 does not exist for transformers since they are not off-the-shelf
 components.
<PctLeakL,3
I.    Enter leakage inductance (% of primary)--SwitcherCAD
 defaults to 1.5%. "Good" transformers can reduce leakage
 inductance below 1%. Lowest cost designs may have 2-4%.
<var1,3
O.    Transformer leakage inductance--Calculated from above.
 As leakage inductance increases, it causes more power dissipation
 in the snubber zener. Leakage inductance can be minimized
 by bifilar winding or by interleaving the primary with the
 secondary.
<Leakvar1,8
O.    Transformer leakage inductance--Calculated from above.
 As leakage inductance increases, it causes more power dissipation
 in the snubber zener. Leakage inductance can be minimized
 by bifilar winding or by interleaving the primary with the
 secondary.
<Rprisel,3
I.    Enter primary series resistance--Initial calculation
 based on % copper loss and RMS primary switch current.
<Rsec1sel,3
I.    Enter secondary #1 resistance--Initial calculation
 based on % copper loss and RMS secondary #1 current.
<Rsec2sel,3
I.    Enter secondary #2 resistance--Initial calculation
 based on % copper loss and RMS secondary #2 current.
<Rsec3sel,3
I.    Enter secondary #3 Resistance--Initial calculation
 based on % copper loss and RMS secondary #3 current.
<C251,3
O.    Operating mode at full load current--"Cont" or "Discont"
 indicates whether the regulator is in continuous or discontinuous
 mode at full load current.
<C226,8
O.    Operating mode at full load current--"Cont" or "Discont"
 indicates whether the regulator is in continuous or discontinuous
 mode at full load current.
<C252,3
O.    Duty cycle--SwitcherCAD calculates operating conditions,
 including duty cycle, at minimum input voltage. Duty cycles
 above 50% will affect maximum available load current when
 using current-mode switchers, such as the LT1070/LT1170
 families.
<C227,8
O.    Duty cycle--SwitcherCAD calculates operating conditions,
 including duty cycle, at minimum input voltage. Duty cycles
 above 50% will affect maximum available load current when
 using current-mode switchers, such as the LT1070/LT1170
 families.
<IswMaxVinL,3
O.    Max rated switch current at this duty cycle--See above.
 Maximum available switch current drops about .67% for each
 1% increase in duty cycle above 50% for the LT1070/LT1170
 family regulators.
<ILpkVinL,3
O.    Peak primary/switch current--This current must be lower
 than the maximum-rated switch-current limit in order to
 ensure that the IC is being operated within specifications.
<Icrit,3
O.    Output current at crossover--SwitcherCAD calculates
 the load current at which the regulator is operating at
 the boundary between continuous and discontinuous modes.
 At high input voltage, the regulator will be in discontinuous
 mode at higher load currents. Unless transient response
 is critical, shifting to discontinuous mode does not affect
 the performance of the regulator.
<C256,3
O.    Is max switch current exceeded?--Peak switch current
 is compared to maximum-rated switch current at the operating
 duty cycle (see above) to ensure that the IC is being operated
 within its specifications. If the rated switch-current limit
 is exceeded, a "Yes" is displayed here. If this occurs,
 a larger primary inductance value an IC with a higher switch
 current rating must be used.
<C231,8
O.    Is max switch current exceeded?--Peak switch current
 is compared to maximum-rated switch current at the operating
 duty cycle (see above) to ensure that the IC is being operated
 within its specifications. If the rated switch-current limit
 is exceeded, a "Yes" is displayed here. If this occurs,
 a larger primary inductance value an IC with a higher switch
 current rating must be used.
<MaxDCe,3
O.    Is max duty cycle exceeded?--If the IC's maximum duty
 cycle has been exceed, a "Yes" is displayed here. LTC switchers
 have a maximum duty cycle of 80%-90% depending on the particular
 part type; refer to Table 3.3.2.
<C267,3
O.    Switching frequency--Repeated here for convenience.
<C268,3
O.    Primary inductance--Repeated here for convenience.
<C269,3
O.    Primary peak current--The selected transformer must
 not saturate at this current level.
<C270,3
O.    Primary ripple current--Peak-to-peak ripple current
 depends mostly on switching frequency and inductance value.

<C271,3
O.    Primary RMS current--The worst-case RMS current occurs
 at the minimum input voltage because this is where the peak
 current is highest.
<C272,3
O.    Secondary #1 RMS current--See "Primary RMS current"
<C273,3
O.    Secondary #2 RMS current--See "Primary RMS current"
<C274,3
O.    Secondary #3 RMS current--See "Primary RMS current"
<C275,3
O.    Output #1 turns ratio (NSec1/NPri)--Repeated here for
 convenience.
<C276,3
O.    Output #2 turns ratio (NSec2/NPri)--Computed from output
 #2 voltage, factoring in diode losses.
<C277,3
O.    Output #3 turns ratio (NSec3/NPri)--Computed from output
 #3 voltage, factoring in diode losses.
<ICRMSVinL,3
O.    Input capacitor RMS ripple current--This is an extremely
 important parameter because it determines the physical size
 of the input capacitor, which may be one of the largest
 components in the regulator. Worst case RMS capacitor current
 occurs at the minimum input voltage.
    SwitcherCAD will select multiple capacitors from the
 database if the input capacitor's RMS ripple current exceeds
 the maximum ripple-current rating of the capacitors in the
 database. Paralleling allows sharing of the ripple current
 between capacitors. See Appendix A for further details.

<ICESRsel,3
I.    Enter input capacitor ESR--This value is used to calculate
 power loss in the input capacitor for efficiency calculations.
 If the database does not contain an appropriate filter capacitor,
 the program selects an ESR of 0.
<ICValsel,3
I.    Enter input capacitor value--The actual value of the
 input capacitor in microfarads is not important, because
 the capacitor is assumed to be purely resistive at switching
 frequencies. SwitcherCAD uses this value simply for the
 parts list printout. If the database does not contain an
 appropriate value, the program selects a value of 1,000,000mF.
Output Capacitor #1 Selection
<OCRMSVinL,3
O.    Output capacitor #1 RMS ripple current--This is an
 extremely important parameter because it determines the
 physical size of the output capacitor, which may be one
 of the largest components in the regulator. Worst case RMS
 current occurs at the minimum input voltage.
    SwitcherCAD will select multiple capacitors from the
 database if the output capacitor's RMS ripple current exceeds
 the maximum ripple-current rating of the capacitors in the
 database. Paralleling allows sharing of the ripple current
 between capacitors. See Appendix A for further details.
<OCESRmax,3
O.    Output-capacitor ESR for ripple voltage--This is the
 ESR (effective series resistance) needed in the output capacitor
 to meet the ripple voltage specification without requiring
 an additional output filter. For low output-ripple specifications,
 the ESR may be unreasonably low and a filter will be needed.
 Keep in mind that electrolytic capacitor ESR is very temperature
 dependent, increasing dramatically at low temperatures.
<OCESRsel,3
I.    Enter output-capacitor ESR--Actual ESR of the chosen
 output capacitor can be entered here. If the database does
 not contain an appropriate value, the program selects an
 ESR of 0.
<OCValsel,3
I.    Enter output capacitor value--The actual value of the
 output capacitor in microfarads is not important, because
 the capacitor is assumed to be purely resistive at switching
 frequencies. SwitcherCAD uses this value simply for the
 parts list printout. If the database does not contain an
 appropriate value, the program selects a value of 1,000,000mF.
 Also, this value will be the sum of all capacitors if SwitcherCAD
 selects multiple capacitors to meet the RMS ripple current
 requirement (See parts list printout).
<OutPPvar1,3
O.    Output ripple (p-p) without filter--Ripple voltage
 is calculated using the ESR from above. Calculations are
 done at minimum input voltage, which is the worst-case condition
 for output ripple in this topology. Don't forget that capacitor
 ESR increases significantly at low temperatures.
<OutFilterReq,3
O.    Is an output filter required?--The output-ripple voltage
 limit is compared to the output ripple without a filter
 (see above) and if the output-ripple voltage limit is exceeded,
 a "Yes" is displayed here.
<FilterAtt1,3
O.    Filter attenuation ratio needed--If an output filter
 is needed, SwitcherCAD divides the unfiltered output ripple
 by the specified output voltage ripple to obtain the required
 attenuation.
<FCCdata,3
O.    Suggested Filter Capacitance from database--SwitcherCAD
selects a filter capacitor using the formula 40uF(IOutMax + 0.5). This
 formula is a rule of thumb used by LTC and represents a compromise
 between capacitor size and regulator transient response.
 The capacitance is used only for calculating the filter's
 resonant frequency.
<FCC,3
I.    Enter Filter Capacitance --SwitcherCAD enters the
selected database capacitor here (see above). This value can be
changed if an alternate capacitor is selected. The
capacitance value is used only for calculating the filter's
 resonant frequency.
<FCESRdata,3
O.    Enter filter capacitor ESR--SwitcherCAD enters the
 chosen capacitor's ESR (see above). For sudden changes in
 load current the ESR of this capacitor allows the output
 voltage to shift. If the output voltage variation is unacceptable,
 then a capacitor with lower ESR should be chosen. Refer
 to the LC output filter section for further details.
<FCESRsel1,3
I.    Enter filter capacitor ESR--SwitcherCAD enters the
selected database capacitor ESR here (see above). This value can be
changed if an alternate capacitor is selected.
<FLmin,3
O.    L needed for output ripple--This is the inductance
 value required to obtain the calculated filter attenuation.
 Rod- or drum-shaped inductors may be substituted for more
 expensive toroids in the LC output filter, because ripple
 current is usually low enough to avoid magnetic-field radiation
 problems.
<FLsel,3
I.    Enter actual L selected--SwitcherCAD selects the smallest
 inductor in the database that has the required inductance
 and is rated to handle full load current.
<C287,3
O.    Output ripple voltage after filter--Actual output ripple
 is calculated using the LC filter capacitor ESR and the
 inductance selected above.
<C289,3
O.    Resonant frequency of filter--This frequency is calculated
 to allow comparison to the frequencies of dynamic loads.
 At the resonant frequency, the filter's output impedance
 is at its maximum.
<C262,8
O.    Output ripple voltage after filter--Actual output ripple
 is calculated using the LC filter capacitor ESR and the
 inductance selected above.
<C264,8
O.    Resonant frequency of filter--This frequency is calculated
 to allow comparison to the frequencies of dynamic loads.
 At the resonant frequency, the filter's output impedance
 is at its maximum.
    Output capacitor #2 selection (see "Output capacitor
 #1 selection," above)
    Output capacitor #3 selection (see "Output capacitor
 #1 selection," above)
<IswIpkVinL,3
O.    Peak switch current--transferred from a previous line
 and displayed here for informational purposes.
<IswAvgVinL,3
O.    Average switch current during on-time--The worst-case
 condition occurs at the minimum input voltage.
<PIC,3
O.    Power dissipated in IC--This is the total power dissipated
 in the IC, including power from quiescent current, switch-on
 voltage, switch rise and fall times, and the switch driver.
 The worst-case condition often occurs at the minimum input
 voltage, where switch-conduction losses dominate IC dissipation.
<TjICMax,3
O.    Maximum-rated IC junction temperature--Transferred
 from the Design Specification screen.
<ThetaJAIC,3
I.    Thermal resistance of IC JA--Junction-to-ambient thermal
 resistance is transferred from the database.
<ThetaJCIC,3
I.    Thermal resistance of IC JC--Junction-to-case thermal
 resistance is transferred from the database. No external
 heatsink is assumed.
<C362,3
O.    Is an IC heatsink required?--IC junction temperature
 is calculated assuming no external heatsink. If the maximum
 junction temperature is exceeded, a "Yes" is displayed here
 and a heatsink must be added in order to meet the IC's maximum
 junction-temperature requirement.
<C336,8
O.    Is an IC heatsink required?--IC junction temperature
 is calculated assuming no external heatsink. If the maximum
 junction temperature is exceeded, a "Yes" is displayed here
 and a heatsink must be added in order to meet the IC's maximum
 junction-temperature requirement.
<RICThetaCA,3
O.    Max thermal resistance of IC heatsink--If a heatsink
 is required, SwitcherCAD calculates the heatsink thermal
 resistance using IC power dissipation and junction-to-case
 thermal resistance. This heatsink is the bare minimum required
 for reliable operation, and will result in the IC operating
 at its maximum-rated junction temperature. We strongly recommend
 that a larger heatsink be used if the regulator is expected
 to operate at maximum load current for extended periods.
<ThetaCAICHS,3
I.    Enter thermal resistance of heatsink--The value calculated
 above is initially displayed here, but the user should enter
 the actual value for the selected heatsink.
<TIC,3
O.    IC temperature at max ambient temperature--IC-junction
 temperature is calculated using the actual heatsink thermal
 resistance entered above.
<Id1AvgVinL,3
O.    Average diode current--For this topology the average
 diode current is always equal to the output current and
 is therefore independent of input voltage, but peak diode
 current (see below) can be many times higher.
<Id1pkVinL,3
O.    Peak diode current--Peak diode current is the sum of
 average current during switch on-time and one-half of the
 peak-to-peak inductor ripple current. This is included primarily
 for informational purposes. Peak diode current may be many
 times higher than the output current.
<IdAvgOnVinL,3
O.    Average diode current during on time--In this case,
 "on time" refers to the period when the diode is conducting,
 rather than to switch on-time. Diode current during this
 period can be much higher than load current, so caution
 must be used in selecting the diode. SwitcherCAD selects
 an output diode by adding the average diode current during
 on-time to the output current and then dividing it by two.
 This is more conservative than simply using output current,
 but it doesn't guarantee reliable operation with continuous
 overloads or shorts. The worst case condition occurs at
 the minimum input voltage.
<Id1VrmaxVinH,3
O.    Max diode reverse voltage @VinH--For this topology
 it is equal to the maximum input voltage times the turns
 ratio plus the output voltage.
<C374,3
O.    Suggested diode type--If the diode's maximum reverse
 voltage is less than 40V SwitcherCAD selects a Schottky
 diode with a forward voltage drop of 0.5V. Otherwise, a
 silicon diode is chosen with a forward voltage drop of 0.8V.
<C348,8
O.    Suggested diode type--If the diode's maximum reverse
 voltage is less than 40V SwitcherCAD selects a Schottky
 diode with a forward voltage drop of 0.5V. Otherwise, a
 silicon diode is chosen with a forward voltage drop of 0.8V.
<Vf1,3
I.    Diode forward voltage for thermal calc--The forward
 voltage drop of many diodes operating at high current densities
 decreases as ambient temperature is increased, at a rate
 of approximately -1mV/oC. To do a "worst-case" analysis
 of diode's junction temperature, use the actual diode forward
 voltage drop at the maximum operating temperature; otherwise
 the calculated temperature will be artificially high. Enter
 a number here which represents the diode's high-temperature
 forward voltage at a current equal to the average diode
 current during on-time.
    SwitcherCAD indicates that diode dissipation is independent
 of input voltage, because the program assumes a fixed value
 for the diode forward voltage and because average diode
 current is always equal to output current. Actually, diode
 dissipation will be somewhat lower at maximum input voltage,
 because peak diode current is lower and therefore Vf is
 lower. Refer to Appendix D for further details.
<Trr,3
I.    Diode reverse recovery time--If a Schottky diode is
 chosen, the recovery time is assumed to be zero. Otherwise,
 for a silicon diode, SwitcherCAD enters the value from its
 database for the chosen diode.
<Trr1,8
I.    Diode reverse recovery time--If a Schottky diode is
 chosen, the recovery time is assumed to be zero. Otherwise,
 for a silicon diode, SwitcherCAD enters the value from its
 database for the chosen diode.
<Pdiod1,3
O.    Power dissipated in diode--This is the sum of forward
 losses and reverse-recovery losses. SwitcherCAD assumes
 that all reverse-recovery losses are dissipated in the diode,
 whereas in actual operation, some of the losses may be transferred
 to the IC, depending on the diode's turn-off characteristics.
 In SwitcherCAD, the worst-case diode dissipation occurs
 at the maximum input voltage when reverse recovery losses
 are factored in. In an actual circuit, however, it can occur
 at the minimum input voltage, where the diode forward voltage
 drop is highest.
<TjD1Max,3
O.    Max rated diode junction temperature--Transferred from
 the Design Specification screen.
<ThetaJAD,3
I.    Thermal resistance of diode JA--This number is transferred
 from the database and assumes no heatsink. Enter the appropriate
 figure if the diode type is changed.
<ThetaJCD,3
I.    Thermal resistance of diode JC--This number is transferred
 from the database. Enter the appropriate figure if the diode
 type is changed.
<C383,3
O.    Is a diode heatsink required?--Diode junction temperature
 is calculated assuming no external heatsink. If the maximum
 junction temperature is exceeded, a "Yes" is displayed here
 and a heatsink must be added in order to meet the diode's
 maximum junction-temperature requirement. Diode thermal
 resistance is critically dependent on mounting technique,
 especially for axial-lead diodes. Some manufacturers unrealistically
 assume ideal mounting conditions when specifying diode thermal
 resistance. Always consult the diode data sheet carefully
 before committing to a diode type and/or mounting procedure.
<C357,8
O.    Is a diode heatsink required?--Diode junction temperature
 is calculated assuming no external heatsink. If the maximum
 junction temperature is exceeded, a "Yes" is displayed here
 and a heatsink must be added in order to meet the diode's
 maximum junction-temperature requirement. Diode thermal
 resistance is critically dependent on mounting technique,
 especially for axial-lead diodes. Some manufacturers unrealistically
 assume ideal mounting conditions when specifying diode thermal
 resistance. Always consult the diode data sheet carefully
 before committing to a diode type and/or mounting procedure.
<RD1ThetaCA,3
O.    Maximum thermal resistance of diode heatsink--If a
 heatsink is required SwitcherCAD enters the maximum thermal
 resistance based on maximum ambient temperature and junction-to-case
 thermal resistance
<ThetaCAD1HS,3
I.    Enter thermal resistance of diode heatsink--The value
 calculated above is initially displayed here, but the user
 should enter the actual value for the selected heatsink.
<TD1,3
O.    Diode temperature at maximum ambient temperature--The
 diode temperature is calculated at minimum input voltage,
 using the actual value for the heatsink entered in the previous
 line.
    Diode #2 operating conditions--(see "Diode #1 operating
 conditions," above)
    Diode #3 operating conditions--(see "Diode #1 operating
 conditions," above)
<Vzmax,3
O.    Max Zener volts for clipping (5V guardband)--SwitcherCAD
 computes this by subtracting the maximum input voltage and
 a five volt guardband from the maximum-rated switch voltage.
<Vzmin,3
O.    Minimum Zener voltage (Vsnub = 5V)--SwitcherCAD computes
 this by adding 5V to the primary flyback voltage.
<VzSug,3
O.    Suggested Zener voltage--SwitcherCAD takes the average
 of the previous two voltages.
<Vz,3
I.    Select Zener voltage--SwitcherCAD inserts the suggested
 zener voltage. The user can enter a new value, but caution
 must be used. Higher values reduce zener dissipation (honestly),
 but risk switch overvoltage. Lower values protect the switch
 better, but may result in excessive zener dissipation. Average
 zener current rises exponentially as zener voltage approaches
 the primary flyback voltage (Vout/N). The final circuit
 checkout should include a test of the zener current waveform
 to verify zener dissipation.
<PSnub,3
O.    Zener power loss--SwitcherCAD computes the zener power
 loss based on zener voltage, peak switch current, and leakage
 inductance. Worst-case operating condition occurs at the
 minimum input voltage. Zener loss can become significant
 with large primary leakage inductance, or low clipper voltage.
<MaxSWvar1,3
O.    Is Max switch voltage exceeded--A "Yes" is displayed
 if the sum of the maximum input voltage and the selected
 zener voltage exceeds the maximum-rated switch voltage.