Patent ID: 7986175
Filing Date: 2011-07-26
Classification: H03L

Abstract:
1. A spread spectrum control PLL circuit for outputting a spread spectrum clock signal based on an input reference clock signal, comprising: a charge pump circuit configured to switch charging and discharging of a charging current, depending on a phase difference between a feedback clock signal based on an output clock signal of the PLL circuit and the reference clock signal; a loop filter circuit having a filter capacitor which is charged and discharged using the charging current output from the charge pump circuit; a voltage controlled oscillator configured to oscillate at a frequency depending on an input control voltage; and a calibration circuit configured to adjust at least one of one of the charging current of the charge pump circuit and a capacitance value of the filter capacitor and a gain of the voltage controlled oscillator, depending on a frequency of the reference clock signal, wherein the voltage controlled oscillator includes: the calibration circuit includes wherein the calibration circuit includes: the control circuit adjusts the gain of the voltage controlled oscillator based on an output of the comparator.