what is bandwidth of a PLL

The bandwidth of a PLL is the measure of the PLL’s ability to track the input clock and jitter. The closed-loop gain 3-dB frequency of the PLL determines the PLL bandwidth. The bandwidth is approximately the unity gain point for the PLL open loop response.

A high bandwidth PLL provides a fast lock time and tracks jitter on the reference clock source, passing it through to the PLL output. A low bandwidth PLL filters out reference clock jitter, but increases lock time.