Enabling sizing for enhancing the static noise margins

Abstract

This paper suggests a transistor sizing method for classical CMOS gates implemented in advanced technology nodes and operating at low voltages. The method relies on upsizing the length (L) of all transistors uniformly, and balancing the voltage transfer curves (VTCs) for maximizing the static noise margins (SNMs). We use the most well-known CMOS gates (INV, NAND-2, NOR-2) for introducing the novel sizing method, as well as for validating the concept and evaluating its performances. The results show that sizing has not entirely exhausted its potential, allowing to go beyond the well established delay-power tradeoff, as sizing can increase SNMs by: (i) adjusting the threshold voltages (VTH) and their variations (σVTH); and (ii) balancing the VTCs. Simulation results show that this sizing method enables more reliable (i.e., noise-robust and variation-tolerant) CMOS gates, which could operate correctly at very low supply voltages, hence leading to ultra-low voltage/power circuits.