A 0.55V 6.3uW/MHz Arm Cortex-M4 MCU with Adaptive Reverse Body Bias and Single Rail SRAM

Abstract

An ultra-low-voltage (ULV) Arm® Cortex®-M4 MCU in 22FDX technology is presented, operating at 0.55V. The circuit employs adaptive body bias (ABB) in a reverse bias scheme with independent control of NMOS and PMOS device performance and has been implemented using a fully ABB-aware sign-off approach. It contains 256 KiB SRAM based on an area efficient 6T bitcell with ABB capability, enabling single supply operation at 0.55V with high yield. A testchip is validated at wafer test and achieves robust operation at 40MHz frequency with 6.6µW leakage power, 6µW ABB generator power and only 6.3µW/MHz total CoreMark power consumption.