Fully-integrated 57 mV cold start of a thermoelectric energy harvester using a cross-coupled complementary charge pump

This paper presents a low-voltage cold-start architecture for battery-less thermoelectric energy harvesters that achieves fast start-up from an input voltage of 57 mV. The fully-integrated design uses a novel cross-coupled complementary charge pump with clocks generated using an ultra-low voltage ring oscillator to create a fast switching edge that assists in starting an inductive boost converter. The autonomous harvester implemented in a 180 nm CMOS process achieves start-up in 135 ms while consuming only 90 nJ of energy from the harvesting source to start the primary converter. This work demonstrates cold-start of a thermoelectric energy harvester at the lowest input voltage reported to date for a fully-integrated solution.