Analysis of the robustness of the TMR architecture in SRAM-based FPGAs

Non radiation-hardened SRAM-based Field Programmable Gate Arrays (FPGAs) are very sensitive to Single Event Upsets (SEUs) affecting their configuration memory and thus suitable hardening techniques are needed when they are intended to be deployed in critical applications. Triple Module Redundancy is a known solution for hardening digital logic against SEUs that is widely adopted for traditional techniques (like ASICs). In this paper we present an analysis of the SEU effects in circuits hardened according to the Triple Module Redundancy to investigate the possibilities of successfully applying TMR to designs mapped on commercial-off-the-shelf SRAM-based FPGAs, which are not radiation hardened. We performed different fault-injection experiments in the FPGA configuration memory implementing TMR designs and we observed that the percentage of SEUs escaping TMR could reach 13%. In this paper we report detailed evaluations of the effects of the observed failure rates, and we proposed a first step toward an improved TMR implementation.