19.2 A 6.4pJ/Cycle Self-Tuning Cortex-M0 IoT Processor Based on Leakage-Ratio Measurement for Energy-Optimal Operation Across Wide-Range PVT Variation

Wireless sensors for IoT applications have become a prominent computing class and are typically severely power constrained. IoT devices are deployed in a wide range of environments and low power consumption must be guaranteed across a wide temperature range. The combination of dynamic voltage scaling (DVS) and adaptive body biasing (ABB) can achieve minimum total energy per cycle, where dynamic and leakage energy are at an optimal trade-off point [1]. However, due to the dependence of leakage on temperature and workload fluctuations over time, this optimal operating point requires runtime adjustment. Traditional approaches to track an optimal operating point involve repeated measurement of processor power inside a body-bias and supply voltage search loop. However, determining processor power consumption adds significant complexity and/or power overhead since it requires separate measurement of supply voltage and current followed by their multiplication.