FREQUENCY CALIBRATION LOOP

摘要

PURPOSE: A frequency adjustment loop is provided to form a lock state of the frequency adjustment loop within fast time by moving an output frequency of an oscillator to wanting frequency band. CONSTITUTION: An oscillator(140) controls an output frequency according to inputted control bit. A programmable divider(150) divides the output frequency of the oscillator according to varied dividing ratio. A counter unit(110) is inputted an output signal of the programmable divider and a reference frequency. The counter unit measures a clock number of the output signal of the divider in one period of the reference frequency. A frequency detector(120) outputs the value tacking out from the clock number outputted from the counter unit in a standard comparison value to a control bit of the oscillator. The programmable divider decides the divide ratio about the output signal of the oscillator by receiving a feedback the clock number outputted from the counter unit.