| 摘要 |
PROBLEM TO BE SOLVED: To provide a PLL detecting circuit, with which stability in operation in a transient state can be improved, occurrence of malfunctions can be avoided and PLL lock discrimination is performed properly. SOLUTION: Corresponding to a phase error signal SE of a PLL circuit composed of a phase comparator 10, a low-pass filter 20 and a voltage-controlled oscillator 30, it is discriminated as to whether the PLL circuit is in a lock state. The level of the phase error signal SE is compared with two threshold VRL and VRH, and when and phase error signal SE is middle between VRL and VRH, it is discriminated that the PLL circuit is in the lock state but otherwise, it is discriminated that the PLL circuit is out of lock state, so that an accurate and stable PLL lock discriminating signal SK can be outputted. |
