Reduction of current mismatching in the switches-in-source CMOS charge pump

In this paper, the charge pump (CP) based on a switches-in-source architecture is to be improved by gain-boosting amplifiers for phase-locked loops (PLLs). In our design, two differential amplifiers were employed in this CP to reduce the effect of the channel length modulation in MOS transistors. As a result, the up and down currents will be rather independent of the output voltage transformed by the capacitive low pass filter (LPF). This circuit was implemented using TSMC 0.18-μm CMOS technology and was investigated at a power supply of 1.8 V. The measured mismatch was less than 1% for the output voltage ranging from 0.4 to 1.4 V. This result is lower than that of the dynamic current-matching CP with feedback tuning on the same architecture. A comparison will be presented and discussed.