Phase offset cancellation technique for reducing low frequency jitters

摘要

A phase locked loop is comprised of a phase-frequency detector for providing to a charge pump up and down pulse signals having pulse widths proportional to phase differences between a pair of signals applied thereto, apparatus for introducing a relative phase difference between a first clock signal and a second signal to provide the pair of signals, the second signal being synchronized with an output signal of the loop, apparatus for providing a third up or down signal to the charge pump offsetting the effect of the introduced phase difference, and apparatus for obtaining a loop control voltage from the charge pump.