SYNCHRONOUS CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide a synchronous circuit capable of achieving broadband characteristics and low phase noise characteristics with a small area.

SOLUTION: A phase detector 11 detects a phase difference between a reference signal and a feedback signal. Voltage generators 12 and 13 generate voltages based on an output signal of the phase detector 11. A pulse generator 16 generates a pulse signal based on the reference signal. A voltage control oscillator 14 generates an oscillation signal in synchronization with the pulse signal. A frequency divider 15 divides the signal from the voltage control oscillator and generates the feedback signal. The voltage control oscillator 14 comprises: a level shift circuit 14c to shift a voltage level supplied by a voltage generation circuit and a ring oscillator consisting of a plurality of inverter circuits 14a and 14b driven by the voltage supplied by the voltage generation circuit as well as the voltage with the voltage level shifted by the level shift circuit. The pulse signal is supplied to one of the inverter circuits.

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