The Analog Behavior of Digital Integrated Circuits

Abstract

The analog behavior of digital VLSI circuits is investigated. A theory based on nonlinear Thevenin equivalent circuits and RC ladder networks is developed. We obtain closed form expressions for the upper and lower bounds on propagation delay through a string of inverters. We generalize this to multiple-input, multiple-output gates and show that the problem of estimating signal propagation delays in VLSI circuits may be reduced to the problem of summing the step responses of a set of linear RC networks. As well as having implications for a computationally efficient timing simulator, the theory begins the formalization of the fundamental properties of digital integrated circuits.