A 12T Subthreshold SRAM Bit-Cell for Medical Device Application

A Schmitt Trigger based SRAM 12T bit-cell is proposed to operate under optimum-energy supply voltage for medical device application. Therefore, the design of medical device has been more and more important in the scope of today's SoC design. As have shown in the simulation, there always exists an optimum-energy supply voltage point (Vopt) in the SoC system, which normally lies in weak sub-threshold or nearthreshold region. As a result, the robustness problem arises due to the low-power operation. Considering about this degraded robustness, structural change instead of the sizing change is considered in this paper. The proposed design has 45% improvement of the SNM compared to the conventional 6T SRAM bit-cell. Due to the wide hysteresis effect, the proposed design also exhibits more robust to process variations. Its hold margin is 30.2% greater than conventional 6T SRAM. The optimum-energy supply voltage of proposed array (256×16) is 400 mV. At the same time, the power consumption at 400 mV decreases to 16% compared to that at 1200 mV.