Charge pump, phase frequency detector and charge pump methods

摘要

A charge pump being disposed in a phase locking system. The charge pump includes a sourcing element, a draining element and an offset element. The sourcing element is arranged to selectively source a first current into an output terminal of the charge pump according to a first control signal, and the draining element is arranged to selectively drain a second current from the output terminal according to a second control signal. The offset element is arranged to selectively conduct an offset current via the output terminal according to a third control signal, and one of the sourcing element and the draining element is disabled when the phase locking system is in a phase-locked state.