A Simple Hybrid Model for Accurate Delay Modeling of a Multi-Input Gate
Arman Ferdowsia, Jürgen Maierb, Daniel Öhlingerc and Ulrich Schmidc
Embedded Computing Systems Group (E191-02) TU Wien, Vienna, Austria
aaferdowsi@ecs.tuwien.ac.at
bjmaier@ecs.tuwien.ac.at
cdoehlinger@ecs.tuwien.ac.at
ds@ecs.tuwien.ac.at
ABSTRACT
Faithfully representing small delay variations caused by transitions on different inputs in close temporal proximity is a challenging task for digital circuit delay models. In this paper, we show that a simple hybrid model, derived from considering transistors as ideal switches in a simple RC model, leads to a surprisingly accurate model. By analytically solving the resulting ODEs for a NOR gate, explicit expressions for the delay are derived. In addition, we experimentally compare our model’s predictions to SPICE simulations and to existing delay models.
Keywords: Digital Circuit Delay Models, Multi Input Switching.
