A charge pump with reduced current variation and mismatch in low-voltage low-power PLLs

Abstract

A charge pump with excellent current matching and negligible current variation characteristics over wide output voltage dynamic range is proposed, which is simulated in the 0.18μm standard CMOS process with the power supply 1.8V. The proposed charge pump circuit improves current matching by applying a high gain operational trans-conductance amplifier. Negligible current variation is achieved by inducing a negative feedback loop to suppress the channel modulation effect. Compared with conventional charge pump circuit, the current mismatch of the proposed charge pump circuit is less than 0.5% within the output voltage dynamic range from 0.2V to 1.7V, and the current variation is reduced to 0.8% over the output voltage dynamic range from 0.32V to 1.7V. Besides, the average power consumption of the proposed charge pump circuit is about 0.48mW making it suitable for low voltage and low power PLLs.