Phase-locked loop circuit and control method thereof

Abstract

The invention relates to a phase-locked loop circuit and a control method thereof. The phase-locked loop circuit comprises a phase frequency detector, a charge pump, a current lens circuit, a loop filter, a loop filter resistance adjusting circuit, a voltage controlled oscillator, and a frequency divider which are connected with each other in turn, wherein the input end of the current lens circuit receives control current outputted by the charge pump and adjusts the size of the control current; and the loop filter resistance adjusting circuit adjusts a resistance parameter of the loop filter according to digital signals divided by the frequency divider. The phase-locked loop circuit adjusts the loop bandwidth and the damping coefficient of the phase-locked loop circuit through the current lens circuit and the loop filter resistance adjusting circuit, so that the stability of the phase-locked loop circuit is improved.

Description

technical field [0001] The invention relates to a phase-locked loop circuit and a control method thereof. Background technique [0002] Since the concept of phase locking was proposed, it has been widely used in the fields of electronics and communication. Phase Lock Loop (PLL) circuits are widely used in clock generation circuits and communication electronic circuits. Although phase-locked technology has been very maturely applied after decades of development, with the complexity and diversification of electronic products, the application of phase-locked loops has been challenged one after another. Among them, a major challenge in the design of the phase-locked loop is: how to make the phase-locked loop suitable for different peripheral circuits. Usually, the phase-locked loop adopts an off-chip low-frequency crystal oscillator as the input clock, and the purpose of adjusting the output frequency of the phase-locked loop is achieved by adjusting the frequency division num...

AI Technical Summary

Problems solved by technology

[0013] By formula (3) (4), in order to adjust the output frequency of this voltage-controlled oscillator 14, after changing the frequency division number N of this frequency divider 15, the bandwidth in the loop parameter of this phase-locked loop circuit 10 and the damping coefficient will all change, thereby affecting the stability of the entire phase-locked loop circuit 10

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