Variation-Resilient Building Blocks for Ultra-Low-Energy Sub-Threshold Design

This paper presents the design of variation-resilient ultra-low-voltage circuits functioning at MHz-speed. By careful design, robust digital circuits operating in the sub-threshold region are achieved. The paper discusses circuit techniques to obtain building blocks that are able to overcome the high sensitivity to variations and the decreased current ratios in sub-threshold while retaining MHz-performance. The building blocks are successfully implemented in two chips fabricated in 90 nm CMOS technology. Measurements show that the variation-resilient designs are fully functional at ultra-low supply voltages and obtain clock frequencies in the MHz-range and sub-pJ energy consumptions.