Characterization of Half-Select Free Write Assist 9T SRAM Cell

Modern biomedical applications have created a high demand for low power static random access memory (SRAM). In this article, a reliable low power half-select free-write assist 9T (HFWA9T) cell has been proposed. To analyze the impact of process variations on different design metrics, the proposed cell has been compared with other contemporary designs such as feedback-cutting 7T (7T), fully differential 8T (FD8T), and single-ended disturb free 9T (SEDF9T) cells. The HFWA9T cell exhibits 2.87x/3.37x higher read stability or read static noise margin (RSNM) than that of 7T/FD8T and 1.40x/6.55xhigher write ability or write static noise margin (WSNM) than that of FD8T/SEDF9T, 2.90x/2.67xand 1.06x/1.01x/5.05x narrower spread in RSNM and WSNM than that of 7T/FD8T and 7T/FD8T/ SEDF9T cells, respectively. In addition, it shows 1.11x/1.03x narrower spread in read delay (T-RA) than that of FD8T/SEDF9T and 1.33x shorter T-RA than that of SEDF9T cell. Furthermore, it consumes only 0.67x/0.31x/0.48x of the write power and 0.262x/0.605x/0.90x of the read power, respectively, consumed by 7T/FD8T/SEDF9T, while consuming 0.34x/0.96x of static power consumed by 7T/FD8T cell. For all these improvements, it incurs a penalty of 1.62x/1.78x in write delay (T-WA) compared to 7T/SEDF9T and 1.58x/1.58x in T-RA compared to 7T/FD8T cell at V-DD = 700 mV.