Event-driven asynchronous voltage monitoring in energy harvesting platforms

Achieving high energy efficiency harvesting platforms requires tracking variations of the energy levels. Leveraging energy storage components whose voltage level varies with the state of charge, it becomes efficient to perform voltage monitoring. In this paper, we propose two types of analog-to-digital voltage monitoring interfaces. In both cases, their outputs directly fit asynchronous 4-phases protocol and Quasi Delay Insensitive (QDI) logic. On the one hand, in a passive voltage monitoring scheme, the platform waits for energy-events. Reacting to voltage threshold crossings, data-events are generated and sent to the asynchronous controller. On the other hand, in an active scheme, the platform waits for an asynchronous data-event before evaluating the voltage level. The analog structure is thus included into the asynchronous protocol and provides a controlled voltage monitoring. These innovative structures allow the voltage monitoring power consumption to be under 300 nA at 0.8 V and to be functional in a wide supply voltage range up to 1.8V.