AN 958: Board Design Guidelines

ID 683073
Date 6/26/2023
Document Table of Contents Thevenin Parallel Termination

An alternative parallel termination scheme uses a Thevenin voltage divider (refer to Figure 31). The terminating resistor is split between R1 and R2, which equals the line impedance when combined. Although this scheme reduces the current drawn from the source device, it adds current drawn from the power supply because the resistors are tied between VCC and GND.

Figure 31. Thevenin Termination

Stub length is dependent on signal rise and fall time and should be kept to a minimum. If your design requires a long termination line between the terminator and receiver, use fly-by termination or Thevenin fly-by termination. Refer to Figure 31 and Figure 32.

Figure 32. Thevenin Fly-By Termination