How to calculate Capacitor value for AC Coupling.

Hie,

Apologies for the delayed first response. The typical response time is within 24 hours, but this case was assigned to me and it was a delay from my part to provide response in time.

The Input Impedance of the dedicated REFCLK pins of the FPGA is 100ohms. This is available in the datasheet

Refer to Table 21, listed as ON-chip termination resistors)

https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/hb/cyclone-v/cv_51002.pdf

I hope this answers your question. Do let me know, if you have further question, I will provide an update as soon as possible.

Regards,

Nathan