PCIe interlane length matching

Autonomous Machines Jetson & Embedded Systems Jetson AGX Orin
,
1

Hello,

I’m designing a board and using UPHY RX/TX 12 ~ 19 as a x8 bus.

Similarly, I’m also using UPHY RX/TX 22,23,10,11 as a x4 bus.

Is there any requirement for length matching between the lanes in the same bus?

Usually we have requirements for length matching all TXs and all RXs in the same bus, but I can’t find them in the Design Guide.

Best regards.

2

You are supposed to have read both the PCI Express Base Specification Revision 4.0 and the PCI Express Card Electromechanical Specification Revision 4.0. The latter says in section 4.7.5 “Lane-to-Lane Skew”:

Skew System Board: Value 1.25 ns: Estimates about a 7-inch trace length delta on FR4 boards.

7 inch delta is hard to reach.

For add-in cards the allowable skew is 0.35ns or 2 inch.

3

This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.