A 595pW 14pJ/Cycle microcontroller with dual-mode standard cells and self-startup for battery-indifferent distributed sensing

Abstract

Battery-indifferent sensor nodes require continuous operation in spite of the intermittently available battery energy, and hence require low peak-power operation to fit the fluctuating power made available by the harvester when the battery is out of energy (Fig. 2.6.1). Such harvested power can be very limited (e.g., nW and below) in aggressively miniaturized systems in the millimeter scale, and is typically well below the leakage consumption of the circuit being powered. Recently, purely harvested continuous operation with an on-chip harvester with sub-leakage sub-nW minimum power has been demonstrated for battery-less operation [1], at the cost of drastically lower performance (i.e., clock frequency in the Hz range) and larger energy. On the other hand, conventional miniaturized sensor nodes pursue minimum energy per operation to maximize the battery lifetime [2-6], but are not able to operate in the sub-leakage regime, and are hence unsuitable for purely harvested operation. Hence, existing solutions cannot interchangeably operate in purely harvested and battery-powered mode, as their design targeting minimum power (energy) severely degrades performance and energy efficiency (peak power consumption).