A lock detection circuit with programmable lock precision and lock frequency

Abstract

The invention discloses a locking detection circuit with programmable locking accuracy and locking frequency. In the locking detection circuit, M frequency division is performed on a reference clock, N frequency division is performed on an output clock of a voltage control oscillator (VCO); a counter of which the counting coefficient is related to M and N is enabled to count with the count value as Cnt for time T2 on an N frequency division signal of the VCO output clock within half a period T1 of an M frequency division signal of the reference clock; After delay of X VCO clocks, a judging module is used for comparing T1 with T2 and judging whether the VCO output clock and the reference clock meet a predetermined relation within a certain error range; meanwhile, a lock state mark LOCK is output. The locking detection circuit disclosed by the invention provides programmable parameters M, N, Cnt and X; and the locking accuracy and the locking frequency of the locking detection circuit can be adjusted by changing the parameters.

Description

technical field [0001] The invention mainly relates to the field of frequency detection in a phase-locked loop, in particular to a locking detection circuit with programmable locking precision and locking frequency. Background technique [0002] In an integrated circuit, in order to ensure correct timing, many circuit modules can work normally only after the phase locked loop (Phase Locked Loop, PLL) completes frequency and (or) phase locking. Therefore, there must be a PLL loop lock detection circuit to complete the detection of these locked states, and output a corresponding flag signal to start other circuits. Considering the requirements of jitter and frequency following capability, the lock detection circuit is designed to perform lock detection on the frequency relationship between the VCO output clock and the reference clock within a certain range around the target frequency. [0003] Usually, within a certain error range of the target frequency, the lock detection c...

AI Technical Summary

Problems solved by technology

Such a circuit structure forms a definite frequency relationship. When the required locking frequency is fixed, a single corresponding reference clock must be used. The accuracy of the circuit and the locking frequency do not have the ability to adjust under different work requirements, and can only be used exclusively for other clocks. For occasions with fixed frequency value, accuracy and frequency multiple relationship

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