Patent ID: 8412120

Claim:
A phase-locked circuit comprising: a phase-locked section including a voltage controlled oscillator having a capacitance bank and changing oscillation frequency according to voltage information, the phase-locked section phase-locking an oscillating signal of said voltage controlled oscillator to a reference signal; and a calibration section having a voltage correcting function for supplying an appropriate calibration voltage to said voltage controlled oscillator in performing frequency calibration for said voltage controlled oscillator; said calibration section including a counter circuit for counting frequency of the output oscillating signal of said voltage controlled oscillator, a first storage circuit and a second storage circuit for retaining a count result of said counter circuit, a comparator circuit for comparing the count result of said counter circuit with a target frequency, and determining whether the count result of said counter circuit is higher than the target frequency, a control circuit for receiving a result of said comparator circuit, comparing the count result of said counter circuit with a result retained by said first storage circuit, and controlling the capacitance bank of said voltage controlled oscillator, a voltage generating circuit for generating the calibration voltage, and supplying the calibration voltage to said voltage controlled oscillator, and a processing circuit for performing calculation from the count result of said counter circuit and results of said first storage circuit and said second storage circuit, and controlling said voltage generating circuit according to a result of the calculation.