Patent ID: 8461933

Claim:
A frequency calibration device for calibrating an oscillating frequency of a clock signal, the frequency calibration device comprising: a logic unit, for gating the clock signal according to a gating window signal to generate a gated clock signal, wherein the gating window signal is indicative of a gating window; a divider, for dividing the gated clock signal by a divisor in frequency to generate a frequency indication signal, wherein a plurality of output digits of the divider are set to the divisor in a calibration cycle; wherein the frequency indication signal is a most significant bit (MSB) of the plurality of output digits; and a control circuit, for adjusting the oscillating frequency of the clock signal according to a logic level of the frequency indication signal which is checked after the gated clock signal stops oscillating by the gating window, to determine whether the oscillating frequency is faster or slower than a target frequency.