| 摘要 |
A voltage-controlled oscillator outputs a signal of a frequency controlled by a voltage of an input signal, the output signal being used for feedback as an internal change signal. A phase comparator detects a phase difference between the internal change signal and an external reference signal. A charge pump outputs the signal having the voltage based on the phase difference to the voltage-controlled oscillator via a low-pass filter. The charge pump is controlled so that the voltage of the signal input to voltage-controlled oscillator becomes a voltage for oscillating a lock frequency. When instruction of changing the lock frequency is input, and/or a phase inversion of the internal change signal used for feedback in a locking-up operation rendered in response to the instructions is detected, a control is made such that an absolute value of an output current of the charge pump is increased.
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