LNL Annual Report 2008

SRAM-based Field Programmable Gate Arrays (FPGAs) are an attractive solution for many applications where short time-to-market, low-cost for low-production volumes, and in-the-field-programming ability are important issues. One of the few major disadvantages of SRAM-based FPGAs is the sensitivity to ionizing radiation [1-3]. Indeed, also at sea level, neutrons, originating from the interactions of cosmic rays with the atmosphere, and alpha particles, coming from radioactive contaminants in the package and solder material, may alter the content of the configuration memory through Single Event Upsets (SEUs). A change in the configuration memory can modify the implemented circuit, possibly leading to Single Event Functional Interruptions (SEFI). Suitable hardening techniques are therefore needed to mitigate radiation effects in modern FPGAs. Hardening-by-design techniques such as Triple Module Redundancy (TMR) [4] are effective in preserving the design functionality when a SEU occurs. Experimental results are reported by first assessing the sensitivity of modern low-end SRAM-based FPGAs to alpha particles in both static and dynamic tests. Afterwards, we discuss the effectiveness of TMR techniques with different voting schemes in enhancing the system reliability, in the case where multiple errors are present in the configuration memory.