MEMS-PMU Co-Simulation of an Electrostatic Energy Harvesting Interface for Battery-Free IoT Devices

Y.-Y. Huang (Institute of Electronics, NYCU, Taiwan), M. Babka, J. Luci, V. Janicek (Czech Technical Univ., Czech Republic), Y.-T. Liao (Department of Electronics and Electrical Engineering, NYCU, Taiwan), P.-H. Hsieh (Department of Electrical Engineering, NTHU, Taiwan), P.-H. Chen (Institute of Electronics, NYCU, Taiwan)

Battery-free Internet-of-Things (IoT) nodes are essential for long-term sensing where battery replacement is impractical. This work presents a fully autonomous IoT platform monolithically integrated in 180nm CMOS/MEMS processes. The system features an in-plane electrostatic MEMS vibration harvester utilizing a photodiode charging system for initial startup. An interface circuit, based on a Bennet's doubler and consisting of MOSFET-based active diodes, efficiently transfers harvested energy, demonstrating up to a 183% efficiency improvement over passive alternatives. The energy is then processed by a power management unit (PMU) featuring two-dimensional maximum power point tracking (2D-MPPT) and a serial-stacked single-inductor multi-input multi-output (SS-SIMIMO) power stage. The PMU maintains stable 0.8V and 1.2V supply rails with a peak power conversion efficiency (PCE) of 88.8% and a tracking accuracy of 98%. System-level co-simulations validate the feasibility of the integrated architecture for self-sustainable sensing applications.