Source Termination in Trim Module PCB Card Cloning
How Source Terminations in Trim Module PCB Card Cloning can be used in bidirectional link port transmissions between SHARC DSPs. The output impedance of the SHARC driver is approximately 17, and therefore a 33 series resistor is required on each end of the transmission line for proper source termination.
The method shown in below Figure can be used for bidirectional transmission of signals from several sources over a relatively long transmission line. In this case, the line is terminated at both ends, resulting in a dc load impedance of 25. SHARC drivers are
capable of driving this load to valid logic levels.
Single Transmission Line Terminated at Both Ends
Emitter-coupled-logic (ECL) has long been known for low noise and its ability to drive terminated transmission lines with rise/fall times less than 2 ns. The family presents a constant load to the power supply, and the low level differential outputs provide a high degree of common-mode rejection. However, ECL dissipates lots of power.
