Formal Methods Based Synthesis of Single Event Transient Tolerant Combinational Circuits

Recent radiation ground testing campaigns of digital designs have demonstrated that the probability for Single Event Transient (SET) propagation is increasing in advanced technologies. This paper presents a hierarchical reliability-aware synthesis framework to design combinational circuits at gate level with minimal area overhead. This framework starts by estimating the vulnerability of the circuit to SETs. This is done by modeling the SET propagation as a Satisfiability problem by utilizing Satisfiability Modulo Theories (SMTs). An all-solution SMT solver is adapted to estimate the soft error rate due to SETs. Different strategies to mitigate SETs are integrated in the proposed framework to selectively harden vulnerable nodes in the design. Both logical and temporal masking factors of the target circuit are improved to harden sensitive paths or sub-circuits, whose SET propagation probability is relatively high. This process is repeated until the desired soft error rate is achieved or a given area overhead constraint is met. The proposed framework was implemented on different combinational designs. The reliability of a circuit can be improved by 64% with less than 20% area overhead.