Charge pump architecture with reduced medium and high frequency noise

Abstract

The charge pump circuit is a crucial building block of most analog phase synthesizers. Furthermore, it's noise usually dominates the synthesizer's in-band phase noise and can also degrade the out-of-band phase noise due to insufficient suppression. In this paper we present a simple modification to a differential current steering charge pump, without the use of op-amps, which inherently suppress the out-of-band noise by more then 10 dB, allowing simpler and more robust synthesizer architecture.