MISIMO: A multi-input single-inductor multi-output energy harvester employing event-driven MPPT control to achieve 89% peak efficiency and a 60,000x dynamic range in 28nm FDSOI

Harvesting energy from ambient sources is an attractive way to enable net-zero-power operation in small wearables, environmental monitors, and IoT devices. However, the power available from most harvesting sources is low, and is thus often mismatched to the instantaneous demands of wirelessly connected devices, which require up to 10s of mW during radio transmission, and down to mW during sleep. Previous works have suggested utilizing multiple energy harvesting sources to increase extractable power, incorporating a battery as an energy buffer, and processing energy with a single inductor to minimize device volume [1,2]. However, such prior art does not support the generation of multiple independently regulated power domains needed for modern SoCs. While single-inductor multi-output (SIMO) converters have demonstrated multi-domain regulation [3,4], they have not been combined with multi-input harvesting, in part since simultaneous regulation of multiple input sources (for MPPT purposes) and loads with a single inductor is not possible with conventional control techniques.