Capacitor connected between two differential path.

Dear Folk,

I always see a capacitor connected between a high frequency differential pair line. What is the functionality of this capacitor?

Thanks

wccheng

I very rarely see a capacitor in this place, mostly termination resistors. You should tell about the application.

As a filter together with the resistance on the differential lines.
In this way, 1pF capacitor equal to two 2pF capacitors put to each node respectively.

I think it is just for limiting the higher frequency emission if any.
I mean to qualify for the radiation standards.

It can also be filtering purposes...

The value of the capacitor is depending on the frequency in the PCB path?