AC coupling of the oscillator reference clock output to the GTM transceiver Quad reference clock inputs serves multiple purposes:
- Blocking a DC current between the oscillator and the GTM transceiver Quad dedicated clock input pins (which reduces the power consumption of both parts as well)
- Common-mode voltage independence
- The AC coupling capacitor forms a high-pass filter with the on-chip termination that attenuates wander of the reference clock
To minimize noise and power consumption, external AC coupling capacitors between the sourcing oscillator and the GTM transceiver Quad dedicated reference clock input pins are required.