Dual-Mode Switched-Capacitor DC-DC Converter for Subthreshold Processors with Deep Sleep Mode

De Vos, Julien [UCL] Bol, David [UCL] Flandre, Denis [UCL]

Wireless sensor networks motivate the development of ultra-low power nodes based on subthreshold processors. As such applications are highly duty cycled, subthreshold processors must support two modes of operation: active mode and sleep mode in which RAM, timer and interrupt control must nevertheless remain powered on. In this paper, we propose a dual-mode switched-capacitor DC-DC converter to power such subthreshold processors with high efficiencies in both modes. It delivers a 0.4V output voltage from a 1-1.2V input source. Simulations in 0.13μm CMOS technology show that the efficiency reaches 74% on a 100μW load, corresponding to the processor active mode. Adaptive body biasing and adaptive internal clock generation supplied by the output voltage allow the converter to maintain an efficiency of 60% on a load as low as 100nW, corresponding to the processor sleep mode.