A 3.2-pW, 0.2-V Trimming-Less Voltage Reference with 1.4-mV Across-Wafer Total Accuracy

This work introduces a class of voltage references able to operate down to 3.2 pW and 0.2-V supply for energy harvesting with relaxed or suppressed voltage regulation (direct harvesting). Inherent wafer-to-wafer process sensitivity limitations and effect of process corners in deep sub-threshold are mitigated via a selection/combination of circuit replicas driven by a process sensor, at zero testing effort and trimming. A 180-nm testchip shows 1.6% process sensitivity (including wafer-to-wafer variations), 60.7-µV/V line sensitivity, and 34.9-µ V/°C temperature coefficient, leading to 1.4-mV overall accuracy across corner wafers.