Multiple Sharing 7T1R Nonvolatile SRAM With an Improved Read/Write Margin and Reliable Restore Yield

This article presents a new resistive random access memory (RRAM)-based average 7T1R nonvolatile static random access memory (nvSRAM). This multiple sharing (MS) 7T1R uses MS schemes in which some of the transistors play various roles. Therefore, the MS-7T1R can perform a decoupled read, enhance write capability, and improve the restore yield with a small area cost. Furthermore, the MS-7T1R can offer two alternative modes, i.e., a high speed and a stable mode. Compared with existing technologies, such as the previous 6T-based nvSRAMs, the results show that the proposed architecture provides a remarkable restore yield and ~154% improvement in the read static noise margin (at TT corner and stable mode). In addition, the read delay improves by ~23% (at TT corner and high-speed mode). The write "1" problem of the single bitline is effectively resolved with our proposed write strategy. The static write margin of "1" is improved by ~88.6% compared with the conventional 6T (β = 4) at a power of 1.2 V. In addition, dynamic power is effectively reduced by the use of the single bitline and sub-word-line driver technology.