A Power Management Unit With 40 dB Switching-Noise-Suppression for a Thermal Harvesting Array

A high efficiency, maximum power point tracking (MPPT) power management unit (PMU), with 3.6 mmbμW quiescent power, aimed at a thermoelectric generator (TEG) array is presented. The proposed energy harvesting PMU is made up of a boost converter with a cascaded capacitor-less low drop-out (CL-LDO) voltage regulator. The segmented approach allows the PMU to match the TEG array´s changing dynamic series resistance via the boost converter and simultaneously provide voltage regulation with adaptive, high switching noise rejection via the CL-LDO. The boost converter´s switching frequency (fsw) is tracked via a Sense-and-Control loop which modifies the CL-LDO´s power supply rejection (PSR) characteristics to place a notch in the PSR transfer function around the average fsw. Experimental results show an overall system efficiency better than 57% @ 1.6 V output voltage, PSR of 40 dB at fsw, and a notch-tuning range of 15-65 kHz. The total active area is 0.93 mm² in 0.5 μm CMOS.