Charge pump circuit and phase-locked loop circuit

Abstract

The embodiment of the invention discloses a charge pump circuit and a phase-locked loop circuit. The charge pump circuit comprises a charge and discharge module which enters a charge and discharge state or a sampled state under the control of a PFD; the voltage of the filter capacitor is used for controlling the frequency of the VCO; the sampling control circuit generates a control signal according to a PFD output result to control the operational amplifier to be conducted to perform voltage sampling or stop voltage sampling; after the operational amplifier is conducted, the operational amplifier samples voltage at a plurality of charging and discharging connection ends on a charging and discharging path, generates bias voltage according to the sampled voltage and provides the bias voltage to the charging and discharging module; the voltage sampling and holding module samples the bias voltage of the operational amplifier when the charging and discharging module is in a sampled state, and holds the bias voltage and transmits the bias voltage to the charging and discharging module when the charging and discharging module enters a charging and discharging state. Through the scheme of the embodiment, the problem of current mismatching of a current charge pump circuit is solved.

Description

technical field [0001] The embodiment of the present application relates to the charge pump circuit design technology, especially to a charge pump circuit and a phase-locked loop circuit. Background technique [0002] The phase-locked loop (PLL) is an important module in the digital-analog hybrid circuit, which can track the phase and frequency of the input signal and output a low-jitter clock signal. It has become an indispensable module in special chips such as communication system, digital circuit, hard disk drive circuit and CPU (central processing unit). [0003] Charge pumps are widely used in phase-locked loop circuits. The addition of charge pumps can provide infinite loop gain and capture range for the loop. In the phase-locked loop circuit, the charge pump is used to convert the digital signal output by the phase frequency detector (PFD) into an analog signal, and the analog signal controls the frequency change of the voltage-controlled oscillator (VCO). The perf...

AI Technical Summary

Problems solved by technology

[0004] A charge pump structure widely used in engineering is as follows figure 1 As shown in the figure, when S1 and S2 are disconnected, S3 and S4 are closed, and the operational amplifier (OPAMP) makes the voltages at points X and Y consistent with the Vc voltage through feedback, which avoids the next time S1 and S2 are closed. The parasitic capacitances at points X and Y have a charge sharing effect on the voltage of Vc. Although this structure improves charge sharing, it cannot avoid the current mismatch between I1 and I2.

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