Patent ID: 6356159
Filing Date: 2002-03-12
Classification: H03L

Abstract:
A frequency synthesizer comprising:an oscillator that controls the frequency of an output signal according to a voltage control signal, a frequency divider that divides the output signal according to a frequency division value that changes cyclically and generates a comparison signal, a phase comparator that generates a phase difference signal by comparing a phase of the comparison signal and a phase of a reference clock signal, a delay circuit that generates and applies a delay to the phase difference signal, a charge pump circuit that generates a control signal corresponding to the phase difference signal that is output from the delay circuit, a low-pass filter that executes a prescribed wave filtering process on the control signal and outputs a voltage control signal, a compensating circuit that superimposes a compensating current on the control signal according to compensation voltage data, a detecting circuit that detects output time of the control signal from the voltage control signal and output time of the compensating current, and outputs a detection signal, wherein the delay circuit controls the supply of the compensation voltage data to the compensating circuit so that the output time of the control signal and the output time of the compensating current are synchronized.