Advanced Down-Counting Operation in SPICE

One of the most important steps in the circuit design is simulation, which is used to validate the circuit before the physical implementation. Simulation Program for Integrated Circuits Emphasis (SPICE) is a popular and accurate simulator where behavioral models of the circuits are needed in order to perform the simulation. Over the last decade, the digital and mixed-signal circuits have become the most encountered type of circuits, where the up and down counting operations are essential. There is a lot of research on up and down counters in the literature, but only the up-counting operation has been approached in SPICE until now. For this reason, in this article, an advanced down-counting operation modeling technique is proposed, which aims to model an any-number of bits down-counter accurately, focusing on eliminating the limitation given by the number of bits of a down-counter and providing a fast simulation time. The verification of the down-counter model is done using the SPICE-based simulator environment OrCAD Capture.