A 0.7 Mm2 Power Management Unit for Implantable Electroceutical Device with a 91.4 % Peak Efficiency Buck-based Hybrid Step-up and -Down MISIMO Converter

We present a complete power management unit (PMU) for mm 3 -sized implantable electroceutical devices. With small size and high power efficiency, it includes all essential electroceutical PMU functions: wireless power transfer (WPT), multiple voltage regulation, and battery charging. To achieve these, a buck-based hybrid step-up and step-down multi-input single-inductor multi-output (BBH-MISIMO) converter is proposed to achieve high efficiency over a wide range of load currents and conversion ratios in small die area. Optimally designed to have a conversion ratio between 0 to 2 for our system, it regulates multiple power and charges a battery, achieving a peak efficiency of 91.4 %. The PMU, fabricated in a 28-nm process, was integrated into an electroceutical system on chip (SoC). It consumed 0.7 mm 2 of die area and achieved 79.1 % of overall ac-to-dc power efficiency from the receiver input to the BBH-MISIMO output.