A 1-Mb 28-nm 1T1MTJ STT-MRAM With Single-Cap Offset-Cancelled Sense Amplifier and In Situ Self-Write-Termination

Abstract

1T1MTJ spin-transfer-torque (STT)-MRAM is a promising candidate for next-generation high-density embedded non-volatile memory. This paper presents a 1-Mb 28-nm 1T1MTJ STT-MRAM with improved sensing margin and reduced power consumption. An offset-cancelled sense amplifier is proposed, using only a single capacitor, to improve sensing margin and accelerate read speed. To save write power, an in situ write-self-termination method is proposed where the sense amplifier is reconfigured without area overhead to continuously monitor the write operation and shutoff the write drivers as soon as the magnetic transition occurs in the bitcell. A prototype chip achieves 2.8- and 3.6-ns read access time at 25 °C and 120 °C, respectively. The in situ write-self-termination scheme reduces write power by 47% and 60% with 20-ns write access time at 25 °C and 120 °C, respectively.