AN 958: Board Design Guidelines

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

In a series termination scheme, the resistor matches the impedance at the signal source instead of matching the impedance at each load (refer to Figure 37). The sum of RT and the impedance of the output driver should be equal to the Z0. Because Intel device output impedance is low, you should add a series resistor to match the signal source to the line impedance. The advantage of series termination is that it consumes little power. However, the disadvantage is that the rise time degrades due to the increased RC time constant. Therefore, for high-speed designs, you should perform the pre-layout signal integrity simulation with Intel input/output buffer information specification (IBIS) models before using the series termination scheme.

Figure 37. Series Termination