Patent ID: 6806741
Filing Date: 2004-10-19
Classification: H03D

Abstract:
A phase comparator for detecting a phase difference between a first signal and a second signal serving as a reference, comprising:a retiming circuit sampling said first signal at a timing synchronized with said second signal to output a third signal; and a phase comparison unit for passing a current according to the phase difference based on said first, second and third signals, said phase comparison unit including a first current source and a second current source, an output node, a first current control circuit connected between said first current source and said output node and passing a current flown to said output node when a result of an exclusive OR operation between said first signal and said third signal is a first logic level, and a second current control circuit connected between said second current source and said output node and receiving a current flown from said output node when said second signal has a second logic level opposite to said first logic level, said first current control circuit having two switching units connected between said first current source and said output node, and said two switching units being designed to provide said first logic level as the result of the exclusive OR operation between said first signal and said third signal when at least one of said two switching units is turned on according to a predetermined combination of said first signal and said third signal that are input.