LinearView - Product Data & Applications 1/LinearView - Product Data & Applications.iso/fcad/readme.doc

Text File | 1996-07-09 | 7.7 KB | 138 lines

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{*                      F i l t e r C A D   1 . 7 0                         *}
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{*                       BRIEF DOCUMENTATION FILE   July 20, 1990           *}             *}
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INTRODUCTION:

  Welcome to the world of computer aided filter design! FilterCAD was designed
to be easy to use as well as being a very powerful filter design tool.  Please
read at least the beginning of this document before starting the program.

GETTING STARTED:

  If FilterCAD is to be installed on a hard drive system, the correct files
must be copied to the correct directories before it will function correctly.
INSTALL.BAT will automatically install the files where they belong if given
the correct path.  To install FilterCAD, place the distribution disk in a
free floppy drive (A: or B:) and change to that drive.  Then type:


                    INSTALL (drive to install on):(optional path)

and the install program will create the correct sub-directories and copy over
all the required files.  Let's do an example.  Let's say you have a hard drive
called C: and you want to put all filter related programs under a directory
called \FILTERS.  After putting the FilterCAD distribution disk in drive A:,
you would type:
                    INSTALL C:\FILTERS

followed by a carrage return.  If the path \FILTERS already exists, the
install program will try to create it and fail. THIS IS NORMAL and not a
problem.  If the path does not exist, INSTALL will create it and copy all
the correct files over.  Next, you must change over to the new directory and
start FilterCAD.  For our example we would type:

                    C:
                    CD \FILTERS\FCAD
                    FCAD

with each line followed by a return.  FilterCAD will give you some errors
regarding screen drivers.  This is normal since FilterCAD is not yet installed.
Press ENTER (return) several times and you will be in the FilterCAD
configuration menu.  The first thing to do is to set the PATH for the device
drivers.  They should be in the same directory as FilterCAD.
Use selection '7' if you need to make a change. The next thing to do is to
select the type of display adapter that is in the system.  This is done using
selection '1'.  If you had a VGA adapter and wanted 640 x 480 x 16 colors,
you would find the corresponding number next to that selection and type it in.
This is now the basic set up for FilterCAD. All other values will default
to a usable number, however, for your personal preferences you may change
any other aspect of the system environment in this menu.  After you have
completed changing all the set up functions use selection '9' to exit the
configuration menu. You will be asked if you wish to SAVE these changes
to disk.  The first time you do this you must answer 'YES'.  This will
create a file called FCAD.CFG which contains all the configuration
information for your set up.  This file is automatically read each
time FilterCAD starts up.  You can now begin designing filters!


BASIC FILTER DESIGN:

  By now you have correctly configured FilterCAD and are about to begin a
filter design.  If not, please read GETTING STARTED first...  If everything
is up and running, the design process now becomes a 1 - 2 - 3 type procedure.
First you must determine the POLE/ZERO locations. This can either be done
externally and entered into a CUSTOM filter specification or synthesized using
FilterCAD.  To enter known POLE/ZERO locations, select option '1' on the main
menu "DESIGN FILTER" and, using the up/down arrow keys and the SPACE bar,
select the desired profile (high pass, low pass, etc) and a response of
CUSTOM.  Press return and you will be entered into a menu which, again using
the arrow keys, allows you to enter your own POLE/ZERO locations.  After you
have completed this, press ESC (Escape) to return to the main menu.  If you
want to synthesize a filter, this can be done by selecting the appropriate
response (BUTTERWORTH, ELLIPTIC, etc.) and pressing enter.  Now you will be
asked for specific design parameteres.  No defaults are supplied here and if
an invalid number is entered, the program will tell you what is wrong. After
correctly entering all required parameters, the synthesis will begin and
generate all the POLE/ZERO locations for you to generate the required filter
response. Now you have a model to use for graphing or implementing the filter.

GRAPHING A FILTER DESIGN:

  Now that you have a valid design, you may want to look at it and determine
if it will fit your design parameters.  This is done with selection '2'.
When entering the graphing routines, you will see a menu for various selections
of devices and views.  The default settings will work fine in most cases.  If
you choose to change anything, use the UP/DOWN arrow keys and the SPACE bar
just as before.  When you are satisfied with your selections, press ENTER and
FilterCAD will graph the response.  You can also ZOOM IN on any part of
your graph.  This can be done with the arrow keys and the ENTER key.
The '+' key will change the rate at which the cursor moves using the
keys to quicken the cursor movement.  The '-' key will restore it to
one PIXEL movement for accuracy. To ZOOM OUT hit the 'L' key (for LAST VIEW).
IF the zoom time is too slow, you can change the number of points that
are calculated for each graph in selection '6' of the main menu.
It is found under selection '6' of the configuration menu.  The
program will default to 500 points.  For a computer without a co-processor,
this may take awhile.  It can be reduced all the way down to 50 points.  Some
graph quality will be lost as a consequence.

IMPLEMENTING A FILTER DESIGN WITH AN LTC SWITCHED CAP FILTER:

  The last step of the design process is to implement the filter with an LTC
switched capacitor filter.  To start this process, select '3' from the main
menu.  This will place you into the OPTIMIZATION/IMPLEMENTATION menu.  Here
you can OPTIMIZE the filter which will automatically select the best device,
modes of operation, and sort the cascade order. The default setting will do
all of the above automatically. To optimize the design press the letter 'O'.
The program will show you what it did to the design.  Next, you need to
calculate the resistor values used to implement each of the modes.  To do this
press the letter 'I'.  Now you can do several different things.  You can change
the cascade order by using selection 'C', you can edit the device selection
or modes by using selection 'D', you can calculate the resistors using
selection 'R', or you can return to the optimize menu by pressing 'O'.  If you
press 'R' to calculate resistors after we have automatically optimized the
design, all you need to do is press either 'A' for absolute resistor values
(useful for hybrids), or 'P' for 1% resistor values (real life).

PRINTING IT ALL OUT:

  Now that your design is complete, you can generate a report of all the
filter parameters by using selection '7' from the main menu.  Here, all the
system's configuration variables are displayed.  By pressing 'R' for report,
the program will build a consolidated report of your design and send it to
the selected printer.

NOTE THAT A PRINTED APPLICATION NOTE #38 IS AVAILABLE FROM LINEAR TECHNOLOGY
BY CALLING 1-800-637-5545. FOR HELP WITH APPLICATIONS TELEPHONE [phone].

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