Single event transients in combinatorial circuits

Abstract

The single event upset (SEU) mechanism in MOS circuits is normally investigated by Spice-like circuit simulation. The problem is that electrical simulation is time consuming and must be performed for each different circuit topology, incident particle and track.This work presents an accurate and computer efficient analytical model for the evaluation of integrated circuit sensitivity to SEU. The key idea of this work is to exploit a model that allows the rapid determination of the sensitivity of any MOS circuit, without the need to run circuit simulations. To accomplish the task, but single event transient generation and its propagation through circuit logic stages is characterized and modeled.The model predicts whether or not a particle hit generates a transient pulse (bit flip) which may propagate to the next logic gate or memory element. The propagation of the transient pulse through each stage of logic until it reaches a memory element is also modeled. Both duration and amplitude of the transient pulse are attenuated as it propagates through the logic gates. A simple, first order model for the degradation of a transient pulse as it is propagated through a chain of logic gates is also proposed. The model considers the electrical masking properties of the logic gates through which the pulse propagates.Model derivation is in strong relation with circuit electrical behavior, being consistent with technology scaling. The model is suitable for integration into CAD-Tools, intending to make automated evaluation of MOS circuit sensitivity to SEU possible, as well as automated estimation of soft error rate.