Source-switched charge pump with reverse leakage compensation technique for spur reduction of wideband PLL

摘要

A source-switched charge pump (SSCP) with reverse leakage compensation technique is proposed to reduce spur level of wideband PLL induced by the reverse sub-threshold leakage of the charge pump. This technique can set the source–drain voltage of current-source N-type MOS (NMOS)/P-type MOS to be close to zero at off-state of the charge pump and thus reduce the reverse leakage. Compared with the conventional SSCP, only one NMOS capacitor, two CMOS switches and two inverters are added in the proposed charge pump. So, there is negligible extra power and extra area cost. A 0.7–1.6 GHz PLL is designed with the conventional and the proposed charge pumps in 65 nm CMOS process. Simulation results show the proposed SSCP can reduce orders of the magnitude of the reverse leakage without the penalty of current matching, compared with the conventional charge pump. The PLL with the proposed charge pump achieves up to 28 dB spur level reduction.