Enhanced p-Channel Metal-Oxide-Semiconductor Field-Effect Transistor Charge Pump for Low-Voltage Applications

In this paper, a power-efficient two-phase p-channel metal-oxide-semiconductor field-effect transistor (PMOSFET) charge pump with two auxiliary clocks to boost the gate biases of the switching transistors is proposed for low-voltage applications. It can increase overdrive voltages of the switching transistors, preserve low voltage drops within the transistors, and work well at a reduced supply voltage. Simulation results show that the proposed two-stage charge pump improves the voltage gain by more than 30% for 0.35 mu m complementary metal-oxide-semiconductor (CMOS) field-effect transistor (FET) technology and improves the maximum power efficiency by 40% for 0.18 mu m CMOS technology in comparison with Racape and Daga's charge pump. Measurement results show that the voltage gains of the proposed two-stage charge pump are more than 95.7 and 92% at supply voltages higher than 1.4 and 0.7 V for 0.35 and 0.18 mu m CMOS technologies, respectively. A compact model of power efficiency for the proposed charge pump is derived and verified by simulations and measurements. Results show that the power efficiency can be approximately 60% at low supply voltages. (C) 2010 The Japan Society of Applied Physics