MULTI SPREAD RATIO SPREAD SPECTRUM CLOCK GENERATOR

摘要

A spread spectrum clock generator capable of controlling a spread ratio is provided to reduce electromagnetic interference due to the spectrum spread of an output frequency. A phase-locked loop(100) has a loop filter(30), and a modulation circuit section(200) is connected to the loop filter and changes an output current amount periodically according to a time to generate a modulated waveform of hershey-kiss type. The modulation circuit part has a square wave generator(210) generating plural charge pump control drive signals and modulation frequency signals, and a second charge pump(220) outputting an electric current which is periodically varied by the signal output from the modulation circuit part.