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 mm
²
in 0.5 μm CMOS.