PCB High-Speed Signal Design Guidelines: Agilex™ 5 FPGAs and SoCs

ID 821801
Date 11/18/2024
Public
Document Table of Contents

3.5.1. GTS Transceiver Channel Recommendations

  • Minimum 2 inches of PCB Route length to a maximum 4 inches for SOM and carrier board together. You have to evaluate the maximum and minimum routing lengths based on specific stack-up and standards.
  • Pair-pair spacing: 5H (TX-TX, RX-RX), “H” is referenced to the thinner dielectric side.
  • Pair-pair spacing: 9H (TX-RX), “H” is referenced to the thinner dielectric side.
  • Total insertion loss, skew, etc., should meet the requirement of PCIE Gen4 spec.
  • Place the AC coupling capacitors on FPGA TX paths close to the FPGA or connector. Do not place them in the middle of the trace routing. Suggest to run simulation to optimize the cut-out of AC capacitors, as demonstrated in the general design considerations of HSSI section.

Informative:

  • Target Differential Impedance: 85 Ω
  • Differential RL better than -15 dB from 0 to 8 GHz