A Silicon-Proof Controller System for Flexible Ultra-Low-Power Energy Harvesting Platforms

In this paper, a heterogeneous controller system and its first-silicon ASIC implementation are presented, where the use of a programmable NanoController next to a general-purpose microcontroller enables more efficient and flexible power management strategies than typical timer-based, periodical power-up of a single microcontroller in state-of-the-art IoT devices. The NanoController features a compact, control-oriented 4-bit ISA, which is used to continuously pre-process data in order to decide when to power-up the microcontroller required for infrequent complex processing, e.g., encrypted wireless communication. Despite its programmability, the required silicon area and power consumption are very small and enable the use in the always-on domain of SoCs for energy harvesting platforms, instead of much simpler and constrained timer circuits. The first-silicon ASIC implementation of such a controller system using a 65nm UMC low-leakage process is presented and evaluated for a real home automation application intended to operate on harvested energy, i.e., electronic door lock, reducing the average power consumption of reference microcontrollers by up to 20x.