A 45nm 0.5V 8T column-interleaved SRAM with on-chip reference selection loop for sense-amplifier

Abstract

8T bit-cells hold great promise for overcoming device variability in deeply scaled SRAMs and enabling aggressive voltage scaling for ultra-low-power. This paper presents an array architecture and circuits with minimal area overhead to allow column-interleaving while eliminating the half-select problem. This enables sense-amplifier sharing and soft-error immunity. A reference selection loop is designed and implemented in the column circuitry. By choosing one of the two reference voltages for each sense-amplifier in a pseudo-differential scheme, selection loop effectively reduces input offset. 8T test array fabricated in 45nm CMOS achieves functionality from 1.1V to below 0.5V. Test chip operates at 450MHz at 1.1V and 5.8MHz at 0.5V while consuming 12.9mW and 46μW respectively.