Analysis and Design of Charge Pumps for Telecommunication Applications

Abstract : This chapter addresses modern telecommunication integrated circuits from the synthesizer focal point; in particular it concentrates at the analysis and the design of integrated charge pump circuit blocks. It presents an overview of charge pump topologies in addition to a coherent analysis of the associated benefits and shortcomings of all circuit alternatives. Moreover a novel favorable charge pump combining current steering techniques with well utilized unity gain buffers in a novel, noiseless feedback scheme, is introduced to improve on switching speed, inherent charge pump ac noise, dead-zone interval, therefore overall steady state aliased loop noise; while on the other hand this charge pump exhibits superb DC matching characteristics in a wide output voltage range. Furthermore a well documented estimation of the active devices that contributes mostly to the overall charge pump noise performance is presented. Also an associated mathematical analysis concerning the frequency content of the charge pump noise current is given. This proposed topology manifests its applicability to charge pump alternatives, as it is demonstrated by the associated simulation results from a 0.18μm design. Because of the low-noise and accurate properties of this improved charge pump, it is ideally suited to modern telecommunication standards synthesizer realizations.