Charge pump construction for phase lock loop circuit

Abstract

The invention discloses a charge pump structure for a phase-locked loop circuit, which is used to convert the phase difference signal output by a frequency discriminator or phase detector to the voltage signal so that to control the output signal frequency of a VCO(voltage controlled oscillator). The invention is characterized in that the charge bump structure includes two identical buffer units which is used to convert the single end signal to differential signal and can generate two complementary differential signals on the Up signal and Down signal, and a charge and loop filter unit which are formed by two identical charge pump circuits connected in series and are used to convert the complementary differential signal to the voltage signal. The charge pump structure of the invention eliminates the influence of parasitic capacitance, reduces the mismatch degree of the transistor during manufacture and keeps the relative matching of the transistor.

Description

technical field [0001] The invention relates to a phase-locked loop circuit structure applied to image display system pixel clock recovery, in particular to a phase-locked loop circuit charge pump structure with noise suppression capability. Background technique [0002] Phase locked loop circuit (phase locked loop, PLL) is an automatic control circuit system that can track the frequency and phase of the input signal, and track and lock the phase and frequency of the output signal and the input signal, so that the phase and frequency of the output signal Can be fixed at a preset value or range. It is widely used in computers, communications, and consumer electronics products. Its main functions are frequency synthesis, clock or data recovery, and signal error elimination. [0003] Initially, DeBellescize proposed the synchronous detection theory in 1932, and published the description of the phase-locked loop circuit for the first time, but it did not attract widespread atte...

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Problems solved by technology

[0011] In order to solve the problems existing in the charge pump structure of the above-mentioned phase-locked loop circuit, the present invention proposes a charge pump structure applied to the phase-locked loop circuit, which is used to solve the problems caused by the parasitic capacitance of the charge pump and the connection delay in the phase-locked loop circuit. Phase-locked loop noise, causing the output signal of the phase-locked loop to jitter and lose lock

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