Modified Decoupled Sense Amplifier with Improved Sensing Speed for Low-Voltage Differential SRAM

Abstract

A modified decoupled sense amplifier (MDSA) and modified decoupled sense amplifier with NMOS foot-switch is proposed for improved sensing in differential SRAM for low voltage operation at 22 nm technology node. The MDSA and MDSANF both offer notable improvements to read delay over conventional voltage and current sense amplifiers. At an operating voltage of 0.8 V, the MDSA exhibited a reduced delay of 28.6%, 41.79%, 37.74%, 30.94% compared to modified clamped sense amplifier (MCSA), double tail sense amplifier(DTSA), modified hybrid sense amplifier (MHSA) and conventional latch-type sense amplifier (LSA) respectively. Similarly, the MDSANF demonstrated a delay reduction of 26.13%, 39.78%, 35.58%, 28.55% over MCSA, DTSA, MHSA and LSA respectively. To validate the performance, the MDSA and MDSANF are evaluated using the variation in delay and power consumption across various supply voltages, process corners, input differential bit line voltage ( Δ V BL ), bit line capacitance C BL ) and the sizing of decoupling transistors. Monte Carlo simulations were conducted to analyse the impact of voltage threshold variations on transistor mismatch which leads to an increased occurrence of read failures and a decline in SRAM yield. The performance analysis of various voltage and current sense amplifiers is presented along with MDSA and MDSANF. Area consideration for selection of sensing scheme is important and as such layout of MDSA and MDSANF was performed conforming to the design rules and estimated area for MDSA is 0.297 μ m 2 whereas MDSANF occupies 0.5192 μ m 2 .