Voltage Scalable Switched Capacitor DC-DC Converter for Ultra-Low-Power On-Chip Applications

This paper presents a voltage scalable switched capacitor (SC) DC-DC converter which employs on-chip charge- transfer capacitors. The DC-DC converter makes use of multiple topologies to achieve scalable voltage generation while minimizing conduction loss and a technique called divide-by-3 switching to minimize the loss due to bottom-plate parasitics. It also uses automatic frequency scaling to reduce switching losses. The converter employs an all digital control which consumes no static power. The voltage scalable SC DC-DC converter with integrated on-chip charge-transfer capacitors was implemented in a 0.18 mum CMOS process and achieves above 70% efficiency over a wide range of load powers from 5 muW to 1 mW, while delivering load voltages from 300 mV to 1.1 V. The active area consumed by the converter is 0.57 mm².