Comparative analysis of various 9T SRAM cell at 22-nm technology node

Abstract

This article presents a comparative analysis of various 9T SRAM cell at 22-nm technology node. Using Monte-Carlo simulations critical design metrics of various 9T SRAM cells are estimated. UV9T (ultralow voltage 9T SRAM cell) offers shortest read delay and DF9T (disturb-free 9T SRAM cell) exhibits longest read delay. SF9T (supply feedback 9T SRAM cell) offers shortest write delay and DFsub9T (disturb-free subthreshold 9T SRAM cell) shows longest write delay. SF9T consumes lower write power compared to other cells. RSNM (read static noise margin) of DF9T, DFsub9T and UV9T are same and equal to 230 mV as they are read decoupled. Although it is read decoupled, SF9T shows 2.19× lower RSNM due to supply gating. SF9T offers 1.70×, 1.68×, 1.21× higher WSNM compared to UV9T, DF9T and DFsub9T respectively. SF9T benefits from shorter write delay, lower write power consumption and higher WSNM at cost of lower RSNM. The designs offering lower read/write delay, write power, higher WSNM and RSNM are reported, to aid the designer in selecting the best cell depending on specific requirements.