Nwise: an Area Efficient and Highly Reliable Radiation Hardened Memory Cell Designed for Space Applications

In the electronics space industry, memory cells are one of the main concerns, especially in term of reliability, since radiation particles may hit cell nodes and disturb the state of the cell, possibly causing fatal errors. In this paper we propose the Nwise SRAM cell, an area-efficient and highly reliable radiation hardened memory cell for use in high-density memories for space applications. Simulations confirm that the proposed Nwise cell is fully tolerant to single event upsets (SEU) in any one of its nodes regardless of upset polarity. Meanwhile, compared with the RHBD-10T cell, the latest area-efficient radiation hardened memory cell, it has higher robustness: the minimum critical charge of Nwise is 4.1× higher than the minimum critical charge of the RHBD-10T cell. It also shows 23% and 12% improvements in read and write static noise margin (SNM). Furthermore, compared with RHBD-10T, up to 18.4% and 7.0% power savings are obtainable during write and read operations respectively. Nwise is about 2.28× faster than RHBD-10T during the more frequent read operation, with a similar penalty in write time. Finally, Nwise is the first proposed high density and reliable radiation hardened memory cell that has been designed using the 28nm FD-SOI technology node. Index Terms—space applications, radiation hardening, single event upset (SEU), multiple event upset (MEU), SRAM design, 28nm FD-SOI, reliability, soft errors, Nwise cel