PCB Design Guidelines (HSSI, EMIF, MIPI, True Differential, PDN) User Guide: Agilex™ 5 FPGAs and SoCs

ID 821801
Date 8/29/2025
Public
Document Table of Contents

3.1. Impedance Tolerances

  • Strictly control the impedance tolerance of high-speed traces. Generally, you can use ±10% tolerance for stripline impedance. However, a ±7% tolerance is better.
  • Breakout routing usually has limited routing space, which may cause impedance discontinuity. To reduce the impedance discontinuity for better return loss performance, optimize the breakout routing trace geometries.
  • Microstrip channel loss may be higher if the solder mask is lossy, offsetting the benefit of the low-loss PCB material. Microstrip channel generally has higher crosstalk compared to the stripline with the same spacing.