Patent ID: 7855580
Filing Date: 2010-12-21
Classification: H03L

Abstract:
1. A phase comparator comprising: an edge detecting unit to which a reference signal is input and to which a referred signal based on the reference signal is input as a feedback signal, the edge detecting unit detecting an edge of the reference signal and an edge of the referred signal; a phase-difference detecting unit that detects a phase difference between the edge of the reference signal and the edge of the referred signal detected by the edge detecting unit; an input-break detecting unit that detects an input break of the reference signal when an edge of the referred signal is again detected after an edge of the referred signal is detected and before an edge of the reference signal is detected; a predetermined-voltage output unit that outputs a predetermined voltage; and a phase-difference-signal output unit that outputs a phase-difference signal for current control based on the phase difference detected by the phase-difference detecting unit so that the phase difference between the reference signal and the referred signal is decreased, the phase-difference-signal output unit, when an input break of the reference signal is detected by the input-break detecting unit, stopping outputting the phase-difference signal based on the phase difference detected by the phase-difference detecting unit, and outputting as the phase-difference signal the predetermined voltage output from the predetermined-voltage output unit to a loop filter that outputs a control voltage according to the phase-difference signal.