Low power single bitline 6T SRAM cell with high read stability

Abstract

This paper presents a novel CMOS 6-transistor SRAM cell for different purposes including low power embedded SRAM applications and stand-alone SRAM applications. The data is retained by the cell with the help of leakage current and positive feedback, and does not use any refresh cycle. The size of the new cell is comparable to the conventional six-transistor cell of same technology and design rules. Also, the proposed cells uses a single bit-line for both read and write purposes. The cell proposed in this paper consumes less dynamic power and has higher read stability than the standard one. In conventional six-transistor (6T) SRAM cell, read stability is very low due to the voltage division between the access and driver transistors during read operation. In existing SRAM topologies of 8T, 9T and higher transistor count, the read static noise margin (SNM) is increased but size of the cell and power consumption increases relatively. In the proposed technique, the SRAM cell operates by charging/discharging of a single bit-line (BL) during read and write operation, resulting in reduction of dynamic power consumption to only 40% to 60% (best case/worst case) of that of a conventional 6T SRAM cell. The power consumption is further decreased if the switching operational voltage of the bit-line lies between 0.25VDD to 0.5VDD. All simulations are done using 0.18um Technology.