A System-in-Package Based Energy Harvesting for IoT Devices with Integrated Voltage Regulators and Embedded Inductors

Integrated energy harvesting and delivery systems are crucial to the development and distribution of IoT devices, where physical dimensions are as important as efficiency. Current harvesting blocks use regulators with on-board inductors/capacitors to interface between the transducers and the load. A System-in-Package (SiP) with Integrated Voltage Regulator (IVR) and on-package passives provides a compact energy harvesting system. This paper demonstrates that, in a SiP based energy harvesting system, co-design of the regulator circuit and the passives depending on the input characteristics of the transducers, the material properties of the passives, and voltage/power demands of the output loads can maximize efficiency for various applications, and extend lifetime of battery-powered and autonomous IoT devices. This paper presents a system design tool that uses a loss model for pulse-frequency modulation (PFM) boost regulators, design of different embedded inductors, and performs co-analysis to estimate optimal efficiency. The simulation result shows potential of 6% improvement in efficiency by co-designing IVR and inductor, compared to optimizing IVR only for a given inductor.