Design of a CMOS Charge Pump for high-performance phase-locked loop

Conventional CMOS charge pump circuits have some current mismatching characteristics. The current mismatch of the charge pump in the PLLs generates a phase offset. This paper investigates causes of current mismatch of conventional CMOS charge pump and proposes new charge pump circuits. By using an error amplifier and reference current sources, one can achieve a charge pump with good current matching characteristics. And by using the charge removal transistors, one can eliminate charge sharing. It was designed by chartered 0.35um CMOS technology and simulated by Spectre tools. Simulation results show the good current match-ing characteristics.