A Phase Locked Loop Circuit with Lock Detection Function

Abstract

The invention discloses a phase-locked loop circuit with a locking detection function, which relates to the technical field of phase-locked loops. The input ends of the detection circuit are respectively connected to the two input ends of the frequency and phase detector and the output end of the first detection circuit, and the input ends of the third detection circuit are connected to the output ends of the first and second detection circuits and the CLKREF signal end; A detection circuit and a second detection circuit judge whether the phase-locked loop is locked by detecting the phase difference between the CLKREF signal and the CLKFB signal, and the first detection circuit can continuously detect the phase difference after locking to ensure that the phase difference occurs at the feedback clock frequency The real locking state of the phase-locked loop can be correctly judged when it changes; the third detection circuit has the function of judging the loss of lock, and can detect the loss of lock of the phase-locked loop circuit; the lock detection circuit composed of three detection circuits can accurately detect the lock state. The locked and unlocked states of the phase loop.

Description

technical field [0001] The invention relates to the technical field of phase-locked loops, in particular to a phase-locked loop circuit with a lock detection function. Background technique [0002] With the development of integrated circuits, phase-locked loops are widely used in chips in various fields to provide accurate and stable clock signals. figure 1 Shown is a basic structure of a phase-locked loop, which consists of a phase frequency detector (PFD, Phase Frequency Detector), a charge pump (CP, Charge Pump), a loop filter (LPF, Low-Pass Filter), a voltage-controlled oscillator It is composed of a VCO (Voltage-Controlled Oscillator) and a feedback frequency division module (Module Div). The output terminal of the feedback frequency division module is connected to the input terminal of the frequency and phase detector to form a feedback system. The frequency and frequency are realized by using the feedback principle. Phase synchronization technology control. [0003]...

AI Technical Summary

Problems solved by technology

However, this kind of lock detection circuit may have the problem that the frequency of the feedback clock CLKFB has changed but is still misjudged as the locked state, and most of the phase-locked loop lock detection circuits only have the lock detection function without the lock detection function, and cannot Real-time reflection of the working status of the phase-locked loop

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