PLL LOCK DETECTING CIRCUIT, AND PLL SYNTHESIZER CIRCUIT HAVING THE PLL LOCK DETECTING CIRCUIT

摘要

PROBLEM TO BE SOLVED: To detect whether a PLL circuit is locked properly.;SOLUTION: A PLL lock detecting circuit detects whether the PLL circuit is locked or not. In this case, the PLL lock detecting circuit receives a reference oscillation frequency signal indicative of a reference oscillation frequency supplied from a reference oscillator, a reference frequency signal which is indicative of a reference frequency obtained by dividing the reference oscillation frequency and which is supplied to a phase comparator, and a comparison frequency signal which is indicative of a comparison frequency obtained by dividing a voltage control oscillation frequency supplied from a VCO and which is supplied to the phase comparator. And the PLL lock detecting circuit outputs a lock detection signal indicative of the PLL circuit lock, on the basis of the reference frequency signal and the comparison frequency signal.;COPYRIGHT: (C)2011,JPO&INPIT