Bus terminator eliminates high speed signal distortion

Using its unique Application Specific Discrete (ASDÖ) technology, SGS-THOMSON Microelectronics has produced a bus terminator IC that eliminates signal distortion in laptops memory extension modules, routers, PCs, servers and similar computer and data communications applications that use high speed parallel buses. Known as the RCD16-47B6, the new device integrates 16 resistor, capacitor and Schottky diode line termination circuits in one tiny SSOP20 package. This small package meets the needs with present package migration towards higher density.

At the high speeds used in today's digital systems, copper tracks on printed circuit boards can exhibit the characteristics of transmission lines, giving rise to ringing and reflection phenomena that can distort the signals. The traditional solution to this problem is to terminate each line of the bus by a circuit comprising a 50 Ohm impedance matching resistor, a small capacitor (around 30pF) to prevent DC power dissipation and a shunt diode to damp undershoot caused by any remaining impedance mismatch. For a 16-bit bus, this requires 48 discrete components and 96 solder joints. The RCD16-47B6 allows these to be replaced by a single device, giving reduced assembly costs and increased reliability.

ASD is a proprietary SGS-THOMSON technology that allows conventional discrete structures such as thyristors, triacs, Zener diodes, Schottky rectifiers, resistors and capacitors to be combined into a single monolithic device tailored to a specific application. The key to this capability is a bipolar technology in which both sides of the wafer are masked and processed, allowing current to flow through the bulk silicon. ASD technology thus combines the benefits of integration with the robustness and current handling capability of discrete devices.

The ASD concept can be used to produce custom devices for use in a wide range of automotive, telecom, consumer, industrial and computer applications and it has also been used to develop a range of standard products such as ignition controllers and protection circuits for automotive and telecom applications.

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