An Analysis Framework for Transient-Error Tolerance

Transient or soft errors are an increasing problem in mainstream microelectronics. We propose a framework for modeling transient-error tolerance (TET) in logic circuits. We classify transient errors as critical or non-critical according to their impact on circuit behavior, such as their ability to disturb the internal state for specified periods of time. We introduce a metric called the critical soft-error rate (CSER) as an alternative to conventional SER, and present some analysis strategies based on CSER. This approach employs a new single transient fault (STF) model, which is defined in terms of a temporary stuck-at fault and its associated circuit state. Although basically technology-independent, STFs can be extended with low-level physical attributes. With STFs, we can estimate the transient error probability p_err of a circuit´s nodes, as well as various measures of error susceptibility and TET. We demonstrate the use of STFs with combinational and sequential circuits, including several types of adders. We also present a systematic hardening strategy that uses p_err as a guide to improving TET.