Calibration device for oscillator and method thereof

A calibration device, for calibrating an oscillating frequency of an oscillator, the calibration device comprising:

• a phase locking device, arranged to track a first reference clock generated by the oscillator until a feedback clock is phase-aligned with the first reference clock, and then arranged to track a second reference clock generated by the oscillator until a phase difference between the second reference clock and the feedback clock is a static phase difference, wherein the feedback clock is generated by dividing an output oscillating signal of the phase locking device by a divisor, wherein a frequency of the second reference clock is different from a frequency of the first reference clock with a frequency difference;
• an adjusting circuit, arranged to adjust the divisor into an updated divisor to reduce the static phase difference between the second reference clock and the feedback clock;
• and
• a calibrating circuit, arranged to calibrate the oscillating frequency of the oscillator according to the updated divisor corresponding to the frequency difference.