Re: [SI-LIST] : Does IBIS describe output transition which both MOS turned on?

D. C. Sessions ([email protected])
Thu, 14 May 1998 07:58:46 -0700

Fred Balistreri wrote:
> D. C. Sessions wrote:


> > Without going into the other uses of the v/t curves, they *can* be used
> > to answer the present question, PROVIDED that the test load is heavy
> > enough to be meaningful (A 10Kohm load isn't going to tell us much
> > about the characteristics of a driver with an Rdson of twelve ohms.)
> > The reason that this is so straightforward is that the crowbar
> > current only flows for a brief time when both devices are nearly OFF
> > anyway, so they are in deep saturation and thus the drain currents
> > are pretty much independent of voltage.
> >
> > > One problem I see is that the v/t information by itself does not contain
> > > the current information.
> >
> > Sure they do, it's just Ohm's Law: Id = Vout/Rload

[more snip]

> Id is not crowbar. So you still have to go back to the I/V data and dig
> it out as I already mentioned.

Ummm... no. Because the devices are in deep saturation at crossover, the
v/i curve is pretty flat. All you really need is min( Idp, Idn ); the
crowbar is the lesser of the pullup and pulldown currents.

[Remainder addressed separately by Chris R.]

D. C. Sessions
[email protected]