Accurate Linear Model for SET Critical Charge Estimation

In this paper, we present an accurate linear model for estimating the minimum amount of collected charge due to an energetic particle striking a combinational circuit node that may give rise to a SET with an amplitude larger than the noise margin of the subsequent gates. This charge value will be referred to as SET critical charge (Qset). Our proposed model allows to calculate the Qset of a node as a function of the size of the transistors of the gate driving the node and the fan-out gate(s), with no need for time costly electrical level simulations. This makes our approach suitable to be integrated into a design automation tool for circuit radiation hardening. The proposed model features 96% average accuracy compared to electrical level simulations performed by HSPICE. Additionally, it highlights that Qset has a much stronger dependence on the strength of the gate driving the node, than on the node total capacitance. This property could be considered by robust design techniques in order to improve their effectiveness.