Patent ID: 6130925
Filing Date: 2000-10-10
Classification: H03L

Abstract:
A frequency synthesizer comprising an oscillator for generating external output signals, a frequency divider which generates a comparison signal by frequency dividing the external output signal from said oscillator and cyclically changing its frequency division value,a phase comparing circuit for generating a phase difference signal by comparing the phase of said comparison signal and the phase of a reference clock signal,a charge pump circuit for feeding a control signal complying with said phase difference signal to said oscillator so that the frequency of said external output signal is equal to the frequency of said reference clock signal multiplied by an average frequency division value,an automatic reference correcting circuit for measuring a ripple component originating in a ripple current contained in said control signal, anda ripple correcting circuit forming a compensation current of opposite polarity than said ripple current based on the measured result of said ripple component and superimposes it on said control signal.