AN 958: Board Design Guidelines

ID 683073
Date 1/28/2022
Public
Document Table of Contents

5.1.2. Cross Talk Minimization

Crosstalk is the unwanted coupling of signals between parallel traces. Proper routing and layer stack-up through microstrip and stripline layouts can minimize crosstalk.

To reduce crosstalk in dual-stripline layouts, which have two signal layers next to each other (refer to Figure 14), route all traces perpendicular, increase the distance between the two signal layers, and minimize the distance between the signal layer and the adjacent reference plane.

Figure 14. Dual- Stripline Layout

Use the following steps to reduce crosstalk in either microstrip or stripline layouts:

Crosstalk also increases when two or more single-ended traces run parallel and are not spaced far enough apart. The distance between the centers of two adjacent traces should be at least four times the trace width, as shown in Figure 15. To improve design performance, lower the distance between the trace and the ground plane to under 10 mils without changing the separation between two traces.

Figure 15. Separating Traces for Crosstalk
  • Widen spacing between signal lines as much as routing restrictions allow. Try not to bring traces closer than three times the dielectric height.
  • Design the transmission line so that the conductor is as close to the ground plane as possible. This technique couples the transmission line tightly to the ground plane and help decouple it from adjacent signals.
  • Use differential routing techniques where possible, especially for critical nets (i.e., match the lengths as well as the gyrations that each trace goes through).
  • If there is significant coupling, route single-ended signals on different layers orthogonal to each other.
  • Minimize parallel run lengths between single-ended signals. Route with short parallel sections and minimize long, coupled sections between nets.

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