Simulation of Multi-Unit Symbols

I have been looking for a way to simulate multi-unit symbols in KiCad, and there seems to be no way to associate a spice model with a multi-unit symbol. Is this true?

There is a thread in the kicad-developers team mailing list archive entitled “Re: SPICE and multi-unit parts” Message #35583 where this problem is also discussed. They describe the issue as being a problem of one-to-one mapping between symbol and spice model, whereas it should be one-to-many.

One way this might be implemented is to treat units of a symbol as if they were unique components. A spice model associated with a symbol having N units must contain N elements of type ‘SUBCKT’. The first in the file would be associated with symbol Unit-A, the second with Unit-B and so on. Does this seem like a viable approach?

Or is this somehow already supported and there exists some undocumented way to simulate multi-unit symbols with spice?

I haven’t done much with Spice (neither within nor without KiCad), but this does make sense. There are some ICs where the different internal units aren’t all the same. For example transceiver chips usually have at least one receiver circuit and at least one driver circuit.

That said, unless the Spice model is able to simulate crosstalk and/or noise from one unit to another I don’t know if it really is necessary support multi-units. In my example of a transceiver chip, one would have two different symbols, one for receiver and one for driver.

Just a couple uninformed comments for the informed to ignore. :wink:

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You might want to have a look at http://ngspice.sourceforge.net/ngspice-eeschema.html#multi

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