Quadruple and Sextuple Cross-Coupled SRAM Cell Designs With Optimized Overhead for Reliable Applications

Abstract

Aggressive technology scaling makes modern advanced SRAMs more and more vulnerable to soft errors such as single-node upsets (SNUs) and double-node upsets (DNUs). This paper proposes two SRAM cells; the first one is called Quadruple Cross-Coupled SRAM (QCCS) and the second one is called Sextuple Cross-Coupled SRAM (SCCS). The QCCS cell comprises four cross-coupled input-split inverters to keep stored values, and provides self-recoverability from SNUs at low cost. To improve reliability, the SCCS cell uses six cross-coupled input-split inverters to construct a large error-interceptive feedback loop and hence robustly keep stored values. The SCCS cell can self-recover from all possible SNUs and one part of DNUs; for remaining DNUs, a node-separation mechanism is used to avoid their occurrence. Simulation results demonstrate the robustness of the proposed cells. Moreover, compared with the state-of-the-art hardened cells, i.e., NASA13T, RHBD12T, We-Quatro, Zhang14T, QUCCE12T, DNUSRM, QCCM10T, QCCM12T, S4P8N, and S8P4N, the QCCS cell reduces read access time by 17%, write access time by 19%, power dissipation by 4% and silicon area overhead by 10% on average, while the SCCS cell reduces read access time by 44% as well as write access time by 13% on average at the cost of moderate increase in power dissipation and silicon area overhead.