PLL CIRCUIT

PROBLEM TO BE SOLVED: To provide a PLL circuit capable of eliminating the process of trimming by disconnection of wiring for controlling VCO(voltage controlled oscillator) oscillation, quickly stabilizing the oscillation of a VCO and performing quick pull-in. SOLUTION: This PLL circuit is provided with a phase comparator, a charge pump, a low-pass filter(LPF) and the VCO and the phase comparator compares the phases of input signals and the output of the VCO or the frequency divided output. In this case, it is provided with a comparison means for detecting a state where the output signal of the LPF exceeds the upper limit and lower limit of a reference voltage set beforehand, a counter means for decreasing in the case of detecting that the output signal of the LPF exceeds the upper limit of the reference voltage and increasing in the case that it falls below the lower limit of the reference voltage and a decoding means for inputting the counted value of the counter means and generating VCO control signals for controlling the VCO oscillation.