US Patent 7417477 PLL circuit

To a frequency divider having a reset function, a second clock of a frequency N×Y times higher than that of a first clock is inputted. Upon receipt of a signal indicating that the stop of the input clock is detected by a start/stop detection circuit, the frequency divider having a reset function resets the dividing of a frequency. Then, upon receipt of a signal indicating that the resumption of the input clock is detected by the start/stop detection circuit, the frequency divider generates and inputs a third clock to a phase comparator by starting the dividing of a frequency.