A 0.025% DC Current Mismatch Charge Pump for PLL Applications

Charge pump (CP) based PLL is one of the most popular techniques because of its wide capture range and zero static phase offset. An op-amp is used to achieve dynamic current matching in the conventional double op-amp CP. This paper proposes a CP, which adopts simple level shift source follower to match the output voltages of two current mirrors when the output voltage of CP changes. Because one of the high-speed op-amps is deleted, the power consumption and area are cut down without sacrificing the current matching performance. The proposed CP achieves less than 0.025% DC current mismatch with 400 mu A charge pump current under 1.2V supply when the output voltage changes from 0.3V to 0.9V in a standard 55 nm CMOS process.