Spice is a powerful tool for circuit analysis. But it often surprises users with
. holes in its abilities and strange definitions
. lack of industry-wide standards
. the need for the user to model the physics of their circuit, not just draw the schematic

I hope this blog will educate users and promote discussion in these areas.

Using SiC MOSFET Spice models

At this time, Spice does not have a built-in model for the new SiC diodes and MOSFETs.

Device manufacturers are using user defined math equations with custom math functions (.FUNC syntax) and/or the DDT function (both part of PSpice syntax) to describe SiC device behavior.

Somewhat surprisingly, there are no semiconductors in these subcircuit models!

Using all math functions allows us to get models now, but they are not as forgiving in simulation as a model based on circuit components. They don’t “talk back” to Spice the way its built-in components do. And they simulate slower. They work in operating point, DC or Transient simulation but may not work correctly in AC analysis.

In a shameless plug, 5Spice v2.60 has been extended to handle this advanced PSpice syntax that current SiC models are using.

There is a discussion on the 5Spice website on using these models. Suggestions on setting 5Spice's and other Spice's simulation parameters are given.

Cree's SiC MOSFET models
use a bastard mixture of Spice3 and PSpice syntax, mixed even within one line. This presents several challenges to using them in any Spice program but LTSpice. The link shows a minor bit of editing of the model file syntax so the models work in 5Spice.

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