Multi-Bit Read and Write Methodologies for Diode-MTJ Crossbar Array

Abstract

Crossbar arrays using emerging Non-Volatile Memory (NVM) technologies offer high density, fast access speed and low-power. However, the bandwidth of the crossbar is limited to single-bit read/write per access to avoid the selection of undesirable bits. In this work, we propose a technique to perform multi-bit read and write in a diode-MTJ (Magnetic Tunnel Junction) crossbar array. The simulation shows that the biasing voltage of half-selected cells can be adjusted to improve the sense margin during read which in turn, reduces the sneak path through the half-selected cells. Results indicate biasing the half-selected cells by 700mV can enable reading as much as 512bits while sustaining 512×512 crossbar with 2.04 years retention. During write operation, the half-selected cells are biased with a pulse voltage source in addition to V/2 scheme which increases the write latency of these cells and enables writing 2 bits while keeping the half-selected bits undisturbed. The 2bit writing requires pulsing by 50mV to optimize energy.