Variations-tolerant 9T SRAM circuit with robust and low leakage SLEEP mode

Abstract

Design of static random access memory (SRAM) circuits is challenging due to the degradation of data stability, weakening of write ability, increase of leakage power consumption, and exacerbation of process parameter variations with CMOS technology scaling. An asymmetrically ground-gated nine-transistor (9T) MTCMOS SRAM circuit is proposed in this paper for providing a low-leakage SLEEP mode with data retention capability. The worst-case static noise margin and write voltage margin are increased by up to 2.52x and 21.84%, respectively, with the asymmetrical 9T SRAM cells as compared to conventional six-transistor (6T) and eight-transistor (8T) SRAM cells under die-to-die process parameter variations in a 65nm CMOS technology. Furthermore, the mean values of static noise margin and write voltage margin are enhanced by up to 2.58x and 21.78% with the new 9T SRAM cells as compared with the conventional 6T and 8T SRAM cells under within-die process parameter fluctuations.