ModelicaSpice: Dymola/Modelica Library for the Simulation of Analog Electronic Circuits

Introduction

Spice is today the most widely used and most successful simulator of electronic analog circuitry. There exist different dialects of Spice (producers of Spice simulators) that distinguish themselves primarily in their models of active semiconductor components (transistors). The most successful among them are PSpice and HSpice.

Although some of the newer versions of Spice offer capabilities for simulating mixed analog and digital circuitry, all of the conventional Spice systems are closed software systems. Therefore, none of these systems are able to simulate mechatronic (mixed mechanical and electronic) models.

The Dymola/Modelica modeling platform offers itself as an attractive alternative, since this technology allows to mix models encoded in different modeling methodologies easily and elegantly.

For this reason, I developed together with my students a new version of Spice, ModelicaSpice, that is coded entirely in Dymola/Modelica. ModelicaSpice has primarily been developed for transient analysis of electronic analog circuitry. However, the software can also be used for DC and AC analyses.

ModelicaSpice permits to simulate mixed analog and digital circuitry as well as mechatronic systems. ModelicaSpice enables the user also to simulate circuits, the parameter values of which are functions of the ambient temperature. In contrast to other Spice dialects, that permit simulation of the amount of heat generated by the circuit as well as simulating the circuit at different fixed temperature values, ModelicaSpice enables the user to simulate circuits accurately during their heating phase, i.e., away from thermodynamic equilibrium.

Furthermore, ModelicaSpice allows to view arbitrary simulation variables, including those that represent phenomena internal to the semiconductor component models. In contrast, other Spice dialects let the user only look at node potentials and branch currents at the top modeling level.

The semiconductor component models were composed in ModelicaSpice graphically and hierarchically from equivalent circuit diagrams.

Historical Development

• I worked for years as a consultant to Burr Brown, where I was responsible for the maintenance of their Spice software. Among other duties, I was tasked with adding new models of specific semiconductor components, with adding new models of special effects in existing semiconductor models, and with adding new algorithms for improving convergence.

• As maintenance of the software turned out to be rather difficult and very time consuming, the idea came about to design and develop a new version of Spice, based on Dymola, that would prove to be much easier to maintain.

• In 1987, I developed first Dymola models for the description of bipolar junction transistors (BJTs) in Dymola. These models were introduced in chapter 6 of the book Continuous System Modeling. Unfortunately, the Dymola of those days was not yet powerful enough to enable me to simulate these models directly.

• In 1993, Daryl Hild developed a first executable version of the BJT model in his Master Thesis.

• In 1997, Michael Schweisguth developed an improved version of the BJT model in his Master Thesis by use of bond graphs.

• In 2005, I adapted the existing BJT models to the newest version of Dymola/Modelica, and developed additional models for the other semiconductor components: the diode, the MOSFET, and the JFET. The currently available version of ModelicaSpice is based on bond graph technology. It forms part of BondLib. I am currently developing a second separate ModelicaSpice library that is not built on bond graphs. This may be useful, since not all circuit designers are familiar with the bond graph notation.

Most Important Publications

1. Cellier, F.E. (1991), Continuous System Modeling, Springer-Verlag, New York.

2. Hild, D.R., and F.E. Cellier (1994), Object-Oriented Electronic Circuit Modeling Using Dymola, Proc. OOS'94, SCS Object Oriented Simulation Conference, Tempe, AZ, pp.68-75.

3. Schweisguth, M.C., and F.E. Cellier (1999), A Bond Graph Model of the Bipolar Junction Transistor, Proc. ICBGM'99, 4^th SCS Intl. Conf. on Bond Graph Modeling and Simulation, San Francisco, CA, pp.344-349.

Sponsors

• Burr Brown, Inc.

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