Differential Read/Write 7T SRAM With Bit-Interleaved Structure for Near-Threshold Operation

Abstract

Near-threshold voltage ( $V_{th}$ ) operation is an effective method for lowering energy consumption. However, it increases the impact of $V_{th}$ variation significantly, which makes it difficult for previously proposed static random access memory (SRAM) bitcells to achieve high read stability and write ability yields. To achieve these in the near- $V_{th}$ region, a differential 7T SRAM bitcell is proposed in which an additional row-based control signal and an nMOS transistor between the pull-up and pull-down transistors is adopted on one side of the cross-coupled inverter. In addition, the proposed SRAM bitcell can use a bit-interleaved structure without the half-select issue. Compared to differential 10T and 12T SRAM, the proposed differential 7T SRAM achieves 5% and 6% higher SRAM operating frequency and 70% and 23% lower operation energy consumption with a 33% and 49% smaller bitcell area, respectively.