Phase-locked loop lock detector circuit and method of lock detection

摘要

There is provided a phase-locked loop lock detector circuit for detecting a lock or unlock state of a PLL circuit. A synchronization circuit synchronizes a lock window signal with a reference frequency signal. A rising edge detection circuit and a falling edge detection circuit output a state of an error signal at a rising edge of an output signal of the synchronization circuit and at a rising edge of an inverted lock window signal, respectively. A logic circuit performs an AND operation on outputs of the detection circuits, and outputs a signal indicating the lock or unlock state.