A 71% efficient energy harvesting and power management unit for sub-μW power biomedical applications

This paper presents an Energy Harvesting and Power Management Unit (EH-PMU) to power battery-less sub-μW systems-on-chip (SoCs) and wireless sensors for emerging Internet-of-Things (IoT) applications. The EH-PMU can harvest energy from either photovoltaic or thermoelectric sources and provides regulated outputs of 0.5V, 1V, and 1.8V. To reduce the power conversion overhead in < 1μW-power systems and thus to extend the system lifetime, the EH-PMU employs a hybrid architecture consisting of nW-quiescent power switched-capacitor DC-DC converters and low-dropout (LDO) regulators. The platform uses a 1.3nW gate-leakage based voltage reference generator, operational from 0.5V, along with Pulse Frequency Modulation (PFM) control to further lower the quiescent power of the switching regulators. The EH-PMU achieves a peak end-to-end efficiency of 71.1% while powering a 1 μW load in a 0.13μm chip.