A subthreshold dynamic read SRAM (DRSRAM) based on dynamic stability criteria

Abstract

This paper introduces a Dynamic Read SRAM (DRSRAM) architecture for high-density subthreshold RAM applications. DRSRAM performs a dynamic read operation to overcome the poor stability and bitline leakage problem of 6T SRAM cell in sub-threshold region. It is shown that there is fundamental limit for wordline activation time and recovery time under a given cell mismatch and bitline leakage. To verify the proposed technique, a 64×128 bit array of the 6T bit-cell is simulated in 90 nm CMOS technology. The simulation results show a 100% noise margin enhancement at subthreshold region. This design operates down to 300 mV at a 1 MHz clock rate with noise margins as large as 72 mV. This design demonstrates significant improvement in the read stability against the conventional 6T SRAM approach without requiring extra cell transistors.