Regenerative Breaking: Recovering Stored Energy from Inactive Voltage Domains for Energy-efficient Systems-on-Chip

Modern Systems-on-Chip(SoCs) frequently power-off individual voltage domains to save leakage power across a variety of applications, from large-scale heterogeneous computing to ultra-low power systems in IoT applications. However, the considerable energy stored within the capacitance of the powered-off domain is lost through leakage. In this paper, we present an approach to leverage existing voltage regulators to recover this energy from the disabled voltage-domain back into the supply using a low-overhead all-digital runtime control system. Simulation experiments conducted in an industrial 65nm CMOS process indicate that over 90% of the stored energy can be recovered across a range of operating system voltages from 0.4V--1V.