A fully differential charge pump with accurate current matching and rail-to-rail common-mode feedback circuit

A fully differential charge pump is proposed in this paper. It adopts the replica technique to eliminate the effect of channel-length modulation, and the charging and discharging currents can match well in a wide output range. A rail-to-rail common-mode feedback circuit is employed to ensure the large swing of the charge pump unrestricted. The charge pump is designed and fabricated in SMIC 0.18μm CMOS process. The measured reference spur-level is about −73dBc and the in-band phase noise is nearly −90dBc/Hz@1KHz. The power dissipation of the charge pump is only 1mW.