A Timing-Shared Adaptive Sensing Methodology for Low-Voltage SRAM

Lowing static random access memory (SRAM) supply voltage could highly improve energy efficiency, yet energy efficiency still not attains optimal point due to the constraint of the weakest bit-cell, especially in low-voltage SRAM. Adaptive sensing methodology is proposed for the challenge and consists of four elements: Switch unit is built to implement cross-sensing operation, Timing-Shared Decoupling Latch Sense Amplifier (TS-DLSA) allows rapid and successive sensing, the judging module is utilized to trigger the FLAG signal which is for adaptive timing controller to cut off word line (WL). Energy efficiency was obtained by compressing the activation delay of WL compared to global timing scheme. The proposed adaptive sensing methodology was performed with TSMC 28-nm CMOS process, and evaluated in SRAM array of 128x128, 256x256, 512x512, and 1024x1024. Monte Carlo simulation results are formed to confirm that, compared to the global timing scheme, the proposed adaptive sensing methodology has reduced WL activation delay by 75.1%∼41.8% and read operation energy overhead by 77.5%∼30.9% from 0.6V to 1.2V. Compared to the current-latched sense amplifier with a footswitch (FS-CLSA) with proposed adaptive sensing methodology, TS-DLSA with proposed scheme have reduced the WL activation by 4.1%∼10.5% and read operation energy overhead by 15.4%∼23.8% from 256x256 to 2048x2048 at 0.6V. The more cells mounted on the BL, the higher energy revenue gains.