A fully integrated switched-capacitor DC-DC converter with hybrid output regulation

In this paper, we propose a fully integrated switched-capacitor (SC) DC-DC converter with hybrid output regulation that allows a predictable switching noise spectrum. The proposed hybrid output regulation method is based on the digital capacitance modulation for fine regulation and the automatic frequency scaling for coarse regulation. The automatic frequency scaler and on-chip current sensor are implemented to adjust the switching frequency at one of the frequencies generated by a binary frequency divider with change in load current. Thus, the switching noise spectrum of the proposed SC DC-DC converter can be predicted over the entire load range. In addition, the bottom-plate losses due to the parasitic capacitances of the flying capacitors and the gate-drive losses due to the gate capacitances of switches are reduced at light load condition since the switching frequency is automatically adjusted. The proposed SC DC-DC converter was implemented in a 0.13 A mu m CMOS process with 1.5 V devices, and its measurement results show that the peak efficiency and the efficiency at light load condition are 69.2% and higher than 45%, respectively, while maintaining a predictable switching noise spectrum.