High-Efficiency Fully Integrated Switched-Capacitor Voltage Regulator for Battery-Connected Applications in Low-Breakdown Process Technologies

Conventional implementations of fully integrated, battery-connected, switched-capacitor voltage regulators (SCVRs) require either thick-oxide mosfets or stacked thin-oxide mosfets as power switches to sustain the voltage stress induced by a nominal 3.7-V Li-ion battery voltage. These approaches, however, exacerbate power loss, thus unable to achieve good power efficiency. Therefore, this paper proposes a solution to overcome the breakdown issue while improving the power efficiency by using only nonstacked, thin-oxide mosfets. This is realized by using a three-state, low-voltage-stress SCVR with a cross-phase-switching technique to decrease the output impedance and increase the total equivalent capacitance in a multiphase configuration. A prototype 3:1 SCVR is implemented fully on-chip in a standard 130-nm CMOS process. The chip is capable of delivering a maximum load current of 45 mA with an input voltage range from 3.2 to 4 V. Measurement results show 78-80% efficiency over a range of output power 4-28 mW, and a power density up to 38 mW/nF. The measured output ripple is 30-50 mV over a load range of 11-45 mA, and the measured voltage droop is 69 mV with 200-ns settling time under a 13-mA load step.