A 12.4pJ/cycle sub-threshold, 16pJ/cycle near-threshold ARM Cortex-M0+ MCU with autonomous SRPG/DVFS and temperature tracking clocks

IoT requirements are almost as varied as the Things to which they are applied, but common demands are maximum battery life with minimum system cost and physical volume. Sub-threshold operation is promising, but even a single un-optimized or always-on component can eliminate low-voltage gains elsewhere. This work presents a highly integrated sub-threshold capable ARM based MCU with fully integrated multi-mode IVR, always-on power control, and on-chip clock sources, achieving 12.44pJ/cycle active energy (6.3pJ/cycle ideal), 139.4nW standby power (46nW ideal) and 1μW ULPBench power. Simple adaptive circuits are demonstrated to be efficient and correct for standby IVR and active system clocks across 0-70°C.