On the Design of 7/9-Rate Sparse Code for Spin-Torque Transfer Magnetic Random Access Memory

A design of 7/9-rate sparse code for spin-torque transfer magnetic random access memory (STT-MRAM) is proposed in this work. The STT-MRAM using spin-polarized current through magnetic tunnel junction (MTJ) to write data is one of the most promising candidates for the next-generation nonvolatile memory technologies in consumer and data center applications. The proposed code is designed to exploit the asymmetric write failure feature of the STT-MRAM. In particular, 7-bit user-data sequences incoming the encoder is encoded into 9-bit codewords, where the Hamming weights of the codewords are equal to 2 and 4 only. A single look-up table accomplishes encoding, whereas the maximum likelihood decoding is deployed in this work. Simulation results demonstrate that the designed code can provide significant improvements for the reliability of STT-MRAM under the effect of both write and read errors.