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

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

3.5.3. PCIe* Add-in Card Edge Finger

Ensure that you do not place any inner-layer conductors, including ground or power planes, beneath the edge-fingers for a distance of 15 mils when supporting a PCIe Gen4 16.0 GT/s add-in card. You can add inner plane layers beneath any of the edge fingers, provided they extend no more than 2 mm into the edge finger region from the main routing area of the board and are at a minimum depth of 15 mils (0.38 mm) beneath the edge finger copper pads on the surface of the PCB.

Figure 29. Add-in Card Edge-finger Regions with Allowed Inner Layer Plane

Make sure that the distance between the top edge ground fingers and the bottom edge of the ground via pads does not exceed 15 mils for add-in-card ground fingers. Connect the adjacent ground edge-fingers at the lowered via location to improve the ground resonance.

Figure 30. Add-in Card Edge-fingers Indicating Adjacent Ground Vias