Circuit of charge pump

Abstract

The invention provides a circuit of a charge pump. The circuit comprises a charge pump module and a reference control circuit which can generate a charge pump output voltage, a bias voltage module and an error operational amplifier, wherein an output end of the reference control circuit is connected to a positive input end of the error operational amplifier; the reference control circuit is applicable to generation of a basis reference voltage; the error operational amplifier is applicable to comparison of values of the basis reference voltage and a charge pump output voltage, and an upper current source in the charge pump module and the reference control circuit is increased or decreased according to a comparison result; and the bias voltage module is applicable to providing a bias voltage for a lower current source in the reference control circuit and the charge module. A current source with a cascode structure is not adopted, a switch tube is disposed at a source electrode of the current source end, and the error operational amplifier is used to increase the matching degree between the upper current source and the lower current source, so that a current difference between the upper current source and the lower current source in the circuit of the charge pump is smaller than 4%; and under the same power source voltage, stray is improved by 18dBc in comparison with a charge pump with a cascode current source.

Description

technical field [0001] The invention relates to a charge pump circuit, in particular to a charge pump circuit used for current matching in low power supply voltage, and the charge pump circuit is also directly applied to a phase-locked loop circuit in an analog integrated circuit. Background technique [0002] Among the various phase-locked loop structures, the most widely used one is the charge-pump type phase-locked loop structure. This type of phase-locked loop has a large capture range and can achieve zero phase difference when locked, that is, the output signal can be tracked without phase difference. input signal. The charge-pump phase-locked loop is a mixed-signal circuit, and the charge pump is a very important analog circuit module, which can convert the digital level output by the frequency and phase detector into an analog signal. [0003] The basic principle of the charge pump is as figure 1 As shown, it consists of two current sources and two switches. When th...

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Problems solved by technology

[0004] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a charge pump circuit for solving the problem of using a cascode structure current source that will cause an output current when the capacitor is charged and discharged in the low power supply voltage of the prior art. poor match problem

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