Frequency calibration circuit and frequency calibration method

Abstract

In the frequency calibration circuit, the digital phase-locked-loop circuit repeats a calibration operation involving outputting the digital control signal corresponding to a time difference between the first clock signal which is input from the first oscillator and has a first frequency accuracy, and the second clock signal which is input from the second oscillator and has a second frequency accuracy lower than the first frequency accuracy, changing the capacitance of the discrete type capacitor bank in accordance with the digital control signal using the second oscillator as a digital control oscillator, and changing an oscillation frequency of the second clock signal in accordance with the capacitance of the discrete type capacitor bank, thereby calibrating a phase of the second clock signal to a phase of the first clock signal.