A 65nm Sub-Vt Microcontroller with Integrated SRAM and Switched-Capacitor DC-DC Converter

Sub-threshold operation has proven beneficial for energy-constrained systems, as it enables minimum energy consumption in logic circuits during active computation [1], and reduces leakage current in components that must be constantly powered. Previous sub-Vt research, for example a 0.13μm processor with an 8b ALU and 2Kb SRAM [2], has demonstrated substantial energy savings. However, process scaling presents a new challenge in the form of heightened intra-die variation. Efficient power conversion and delivery is another essential consideration for a micro-power system. This paper presents a 65nm sub-Vt SoC featuring a microcontroller core and custom 128Kb SRAM functional in sub-threshold, powered by a switched capacitor DC-DC converter that delivers variable load voltages from 0.3V to 0.6V.