Ultra-Low Power Read-Decoupled SRAMs with Ultra-Low Write-Bitline Voltage Swing

Abstract

We propose an ultra-low power memory design method based on the ultra-low ( $$\sim $$ ~ 0.2 V) write-bitline voltage swing to reduce the write power dissipation for read-decoupled SRAM (RD-SRAM) cells. By keeping the write bitlines at ground level (0 V) during standby and charging them to a low voltage $$V_\mathrm{L}$$ V L ( $$\sim $$ ~ 0.2 V) during write operations, the power dissipation for the write bitlines is greatly reduced (0.2 V/ $$V_\mathrm{DD})^{ 2 }\,\times $$ V DD ) 2 × 100 %) due to reduced voltage swing (from $$V_\mathrm{DD }$$ V DD = 1.2 to 0.2 V) on the write bitlines. The proposed method is applicable to both dual-voltage and single-voltage operations. We analyze the proposed ultra-low write-bitline voltage swing method and investigate its reliability based on 10K Monte-Carlo simulations. We further verify the functionality and performance of our proposed design through measurements on the fabricated prototypes based on the 65 nm CMOS process. By means of a $$256 \times 64$$ 256 × 64 bit RD-SRAM memory implementation, we show that our proposed method reduces 87 % write power dissipation when compared to a conventional design.