Process-Tolerant Ultralow Voltage Digital Subthreshold Design

Abstract

We propose process variation tolerant circuit techniques for robust digital subthreshold design. We present an 8times8 process-tolerant FIR filter, working in both super-threshold and subthreshold regions featuring adaptive beta-ratio modulation and integrated level converters. Ultra-dynamic voltage scaling (UVDS) enables the filter operation at 85 mV consuming 40 nW. For memory applications, we propose Schmitt trigger based SRAM bitcell exhibiting built-in process variation tolerance. Functional SRAM with the proposed memory bitcell is demonstrated at 160 mV in 0.13 mum CMOS technology.