A 300mV Sub-1pJ differential 6T sub-threshold SRAM with low energy and variability resilient local assist circuit

Lowering supply voltage from super-threshold to sub-threshold is a promising approach for ultra-low energy applications. However, the degraded cell stability limits the voltage scalability of the conventional 6T SRAM. In this paper, we proposed a novel local assist circuitry that enables low energy and variability resilient operation at ultra-low voltages for differential sub-threshold SRAM design. The process variation tolerant local sense amplifier and charge-sharing based precharge scheme are utilized to ensure the read stability at ultra-low voltage region. A 16kb 6T SRAM marco is implemented in 90nm CMOS technology to demonstrate the functionality of our proposed local assist circuits. Its minimum energy consumption is 0.624pJ/access, operating at 26.3MHz and 400mV.