Patent ID: 7659760
Filing Date: 2010-02-09
Classification: H03L

Abstract:
1. A phase-locked loop circuit, comprising: a charge/discharge control circuit for outputting a power supply voltage or a ground voltage; a plurality of capacitors; a first switch group including plural switches which are respectively connected to the plural capacitors and which supply selectively the plural capacitors with the output of the charge/discharge control circuit; a second switch group including plural switches respectively connected to the plurality of capacitors; and a control circuit for controlling the charge/discharge control circuit so that it outputs either a power supply voltage or a ground voltage on the basis of the phase difference between a reference frequency signal and the oscillation frequency signal of a voltage-controlled oscillator or an internal clock signal which is obtained by dividing the oscillation frequency signal, and for controlling the selecting of a specific capacitor from among the plural capacitors by turning on and off the first switch group individually, the charging or discharging of the specific capacitor by using the output of the charge/discharge control circuit, and then the sharing of an electric charge with a capacitor, the electric charge being stored in the specific capacitor by turning on and off the second switch group individually, the capacitor retaining a control voltage that controls the oscillation frequency of the voltage-controlled oscillator, or the sharing of the electric charge of the capacitor retaining the control voltage with the specific capacitor.