An efficient thermal energy harvesting and power management for μWatt wearable BioChips

This paper presents an efficient thermal energy harvesting IC (EHIC) that supports a battery-less μWatt system-on-chips. The EHIC consists of an inductor-based DC-DC converter that boosts a low input voltage to a suitable output voltage level. Further, a switched capacitor buck converter is utilized to regulate the boost converter output voltage and to support multiple output voltage levels, namely 0.6V, 0.8V and 1V. In low energy mode and to enhance the efficiency, the EHIC is capable of bypassing the switched capacitor so that the load is driven directly from the boost converter. The prototype chip is fabricated in 65nm CMOS and occupies an area of less than 0.46mm2. Measured results confirm an efficiency of 65% at 0.6V output voltage and 42μW. In addition, the end-to-end peak efficiency is 71% at 0.8V output voltage and 182μW.