Charge pump for eliminating current mismatch and phase-locked loop circuit

Abstract

The invention discloses a charge pump for eliminating current mismatch and a phase-locked loop circuit. The charge pump comprises a first current source, a first MOS transistor, a second MOS transistor, a third MOS transistor, an operational amplifier, a first switch, a second switch, a third switch and a fourth switch. The output end of the first current source is connected with the grid electrode of the first MOS transistor, the drain electrode of the first MOS transistor and the grid electrode of the third MOS transistor, the source electrode of the first MOS transistor is grounded, and thesource electrode of the third MOS transistor is grounded; the drain electrode of the third MOS tube is connected with the second end of the first switch and the second end of the second switch. The drain electrode of the second MOS tube is connected with the first end of the third switch and the first end of the fourth switch, and the grid electrode of the second MOS tube is connected with the output end of the operational amplifier. According to the charge pump for eliminating current mismatch and the phase-locked loop circuit provided by the invention, current mismatch caused by a channel length modulation effect can be effectively reduced; and meanwhile, the charge pump circuit avoids current mismatch caused by manufacturing deviation of a current source in principle.

Description

technical field [0001] The invention belongs to the technical field of electronic circuits, and relates to a charge pump, in particular to a charge pump and a phase-locked loop circuit for eliminating current mismatch. Background technique [0002] Phase-locked loop circuits are widely used in various circuits. They can be used to generate radio frequency clock signals in analog circuits, and can be used to generate reference clocks for digital circuits in digital circuits. The charge pump phase-locked loop has become a classic phase-locked loop implementation with its high performance and low power consumption. [0003] The charge pump is a core module in the charge pump phase-locked loop. The charge pump works together with the frequency and phase detector to extract the error signal of the loop, which is further processed by the loop filter. The performance of the charge pump has a significant impact on the overall performance of the PLL: [0004] (1) The current misma...

AI Technical Summary

Problems solved by technology

[0004] (1) The current mismatch of the charge pump is one of the sources of the phase-locked loop output spurs;

[0005] (2) The current mismatch of the charge pump will cause the nonlinearity of the frequency detector and the charge pump. This nonlinearity will alias the high-frequency noise in the circuit to the low frequency, thereby affecting the noise characteristics of the phase-locked loop;

There are two main advantages of this structure, no additional loops are introduced to cause stability problems, no additional noise sources are introduced to affect the charge pump noise

There are three main disadvantages of this structure. The addition of the common gate tube reduces the voltage variation range of vctrl; an additional bias circuit is required to provide the vcasn voltage and vcasp voltage; the common source common gate structure improves the output impedance in the deep submicron process Limited, current mismatch improvement is limited

There are three main disadvantages of this structure, op2 will introduce additional noise, op2 will consume additional current, and additional compensation capacitors must be added to eliminate the risk of instability

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