Abstract

Reliability assessment is an important part of the design process of digital integrated circuits. We observe that a common thread that runs through most causes of run-time failure is the extent of circuit activity, i.e., the rate at which its nodes are switching. We propose a new measure of activity, called the transition density, which may be defined as the "average switching rate" at a circuit node. Based on a stochastic model of logic signals, we also present an algorithm to propagate density values from the primary inputs to internal and output nodes. To illustrate the practical significance of this work, we demonstrate how the density values at internal nodes can be used to study circuit reliability by estimating (1) the average power & ground currents, (2) the average power dissipation, (3) the susceptibility to electromigration failures, and (4) the extent of hot-electron degradation. The density propagation algorithm has been implemented in a prototype density simulator. Using ...

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