Re: IBIS Series MOSFET Models - questions

Mike,

A while ago I created some Bus switch models. They can be found at:
http://www.fairchildsemi.com/models/ibis/#fst

-Christian

Mike LaBonte wrote:

> Stephen,
>
> The figure in the IBIS specification is electrically equivalent to yours,
> although your version is easier to understand, in my opinion. The spec
> shows two swept sources with a DC offset between them. I prefer your notion
> of one fixed source and one swept source, closer to the hardware that would
> actually be used.
>
> I would like to see the diagrams also showing the attachment of the gate to Vcc,
> since it currently appears that the entire circuit just floats up and down with the
> sweep voltage. Then again, maybe the swept source should be attached between
> the source and gate, since we are attempting to sweep Vgs.
>
> By the way, has anyone found one of these series switch models available for
> public use?
>
> Mike
>
> Stephen Nolan wrote:
> >
> > Question 1,
> >
> > In IBIS Version 3.2, Section 6, "Keyword: [Series MOSFET]" it states that
> > "C_comp values are ignored for [Series MOSFET] models." How do you account for
> > the Cio(off) and Cio(on) characteristics of the FET in the IBIS model?
> >
> > Question 2,
> > In IBIS Version 3.2, Section 6, "Keyword: [Series MOSFET]", and Section 9.5,
> > "Series MOSFET Table Extractions", it says that the voltage applied to the drain
> > of the MOSFET is Vds, a fixed voltage difference between the drain and the
> > source. Quoting from section 9.5:
> >
> > Vds is held constant by having a fixed voltage Vds
> > between the drain and source nodes.
> >
> > However, the drawing shows a fixed voltage source between the drain and GROUND!
> >
> > | +----------------------------------------+
> > | | |
> > | | Ids = Table Current |
> > | | ---> |
> > | +---<---| |--->----------+ |
> > | d |_____| - s | + |
> > | --+-- Vgs +---+---+ +----+----+
> > | | g + | Sweep | | Vs + |
> > | | Vs | |Fixed Vds|
> > | +---+---+ +----+----+
> > | | - |
> > | GND GND
> > |
> > | Example of Series MOSFET Table Extraction
> >
> > I could see how this would result in a Vds voltage if Vs + was swept, so that it
> > was always equal to the swept Vs+Vds, but it says "Fixed", not "Sweep".
> >
> > Shouldn't this drawing be as follows for a true Vds supply?
> > | +---------+
> > | + | Vs + | -
> > | +-----------+Fixed Vds|------+
> > | | +---------+ |
> > | | |
> > | | Ids = Table Current |
> > | | ---> |
> > | +---<---| |--->----------+
> > | d |_____| - s | +
> > | --+-- Vgs +---+---+
> > | | g + | Sweep |
> > | | Vs |
> > | +---+---+
> > | | -
> > | GND
> >
> > --
> > Regards,
> > Stephen M. Nolan