Dynamic Dual-Reference Sensing Scheme for Deep Submicrometer STT-MRAM

As process technology downscales, read reliability has become a critical barrier for spin transfer torque magnetic random access memory (STT-MRAM), owing to the increasing process-temperature-voltage (PVT) variations, decreasing critical switching current of magnetic tunnel junction (MTJ) and supply voltage. To deal with the read reliability challenge, we propose herein a dynamic dual-reference sensing (DDRS) scheme. The key features of the proposed DDRS scheme include: (a) two reference signals, generated by two reference cells with the same structures as those of the data cells, are provided to the sensing circuit; (b) the reference signals are adaptively dynamical depending on the content stored in the target data cell; (c) two output signals are obtained to decide the sensing result, adding redundancy for supporting self-error detection (SED) capability. The proposed DDRS scheme can achieve a great improvement in sensing margin (SM) and bit error rate (BER), in comparison with conventional sensing schemes. In addition, no regularity problems exist in the proposed DDRS scheme, as the reference cells maintain exactly the same structures as those of the data cells. Our simulation results show that the proposed DDRS scheme can achieve a ~ 7× increase in average SM, and a ~ 70% reduction in average BER, compared with conventional sensing schemes.