Twin-Coupled Sense Amplifier to improve margin in 1T-1MTJ based MRAM array

Abstract

Spin Transfer Torque-Magnetoresistive RAM (STT-MRAM) is considered as one of the most promising candidates for universal memory because of its many desirable characteristics such as non-volatility, low read and write power, high endurance, high integration density and CMOS compatibility. However, the narrow gap between low resistance (Rp) and high resistance (Rap) of the STT-MRAM results in smaller sense margin and high read failure probability. Therefore, in this paper, we propose a twin-coupled sense amplifier which uses two parallel sense amplifiers to expand the sense margin. The proposed circuit uses data-dependent reference current during read operation instead of using average of Ip (current corresponding to Rp) and Iap (current corresponding to Rap), which helps in increasing the sense margin by 2x as compared to existing sense amplifiers.