What is the AC coupling capacitor recommendation for E-tile reference clock input?

Description

It is recommended to add external AC coupling capacitors given the E-tile reference clock input buffer structure.

 

Resolution

There are two internal 50ohm terminations that will act as 100ohm parallel termination. See the Intel® Stratix® 10 TX Signal Integrity Development Kit for an example of these capacitors. 

Please refer to E-Tile Transceiver PHY User Guide Figure 64. IO Pad Ring - Transceiver Reference Clock Input Pad.