Importance

Loading Importance Indicators...

Abstract

Phase locked loop (PLL) detection circuit that can improve the stability of operation, avoid occurrence of an erroneous operation, and perform PLL lock judgment correctly. Whether a PLL circuit that consists of a phase comparator, a low-pass filter, and a VCO is in a lock state is judged based on a phase error signal in the PLL circuit. The level of the phase error signal is compared with two threshold values, VRL and VRH. When the phase error signal is somewhere between VRL and VRH, a judgment is made that the PLL circuit is in a lock state. A judgment that the PLL circuit is out of a lock state is made in the other cases. This makes it possible to output a correct and stable PLL lock judgment signal.

Loading the Abstract Image...

First Claim