7.5.1 General Routing Guidelines
To maximize signal integrity, proper routing techniques for differential signals are important for high speed designs. The following general routing guidelines describe the routing guidelines for differential lanes and differential signals.
- As much as possible, no other high-frequency signals must be routed in close proximity to the differential pair.
- Must be routed as differential traces on the same layer. The trace width and spacing must be chosen to yield the differential impedance value recommended.
- Minimize external components on differential lanes (like external ESD, probe points).
- Through-hole pins are not recommended.
- Differential lanes mustn’t cross image planes (ground planes).
- No sharp bend on differential lanes.
- Number of vias on the differential pairs must be minimized, and identical on each line of the differential pair. In case of multiple differential lanes in the same interface, all lines should have the same number of vias.
- Shielded routing is to be promoted as much as possible (for instance, signals must be routed on internal layers that are inside power and/or ground planes).