APPARATUS AND METHOD FOR SMALL SIZE SPREAD SPECTRUM CLOCK GENERATION

摘要

PURPOSE: A small area spread spectrum clock generator and a method thereof are provided to overcome the limit of the bandwidth of phase sync loop which is subordinate in the modulation frequency by additionally forming a demodulator unit and demodulation control unit in order to offset the modulation amount. CONSTITUTION: A line divider unit(40) outputs a reference clock signal by dividing. A phase frequency detection unit(42) outputs the detected result to an error signal by detecting the frequency between the reference clock signal and the compare clock signal and phase difference. A charge pump(44) outputs the current corresponding to the error signal. A loop filter(46) outputs the control voltage corresponding to current. A modulation control unit(52) generates the modulation amount corresponding to the modulation conditioning signal. A modulator unit(48) outputs the modulation result of the control voltage corresponding to the modulation amount. A voltage controlled oscillator(50) outputs the oscillation clock signal with the oscillated frequency as the result of spreading of the band of the external clock signal according to the modulation result. A feedback divider unit(54) outputs the compare clock signal by dividing. A demodulation control unit(70) generates the demodulation amount offsetting the modulation amount. A demodulator(72) offsets the modulation of the control voltage outputted from the loop filter corresponding to the demodulation amount.