[SI-LIST] Re: IBIS model Tr accuracy
- From: "Henson, Bradley S" <Bradley.S.Henson@xxxxxxxxxx>
- To: <a.ingraham@xxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Wed, 19 Oct 2005 09:44:47 -0700
This reminds me of an old, but relevant story.
Back in the early 80's Fairchild had just introduced their FAST advanced
schottky technology. I was seeing extraordinary prop delay push-out
under the various patterns I applied to the other 7 I/O while measuring
1 of them (the worst offenders were like the F244, F245 etc.). Fairchild
said the tpd spec was only valid for a single output switching. DESC
copied their statement in the Mil Drawings. I wrote a letter to DESC
asking how we were supposed to design robust systems using their specs.
I received back an answer from the DESC component Engineer that we could
only count on switching 1 output at a time in our application! I guess
he knew best as he went on to head that branch years later :(
We probably want IBIS models to reflect any combination of I/O patterns
:)
Enjoy
Brad
-----Original Message-----
From: Andrew Ingraham [mailto:a.ingraham@xxxxxxxx]=20
Sent: Wednesday, October 19, 2005 9:30 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: IBIS model Tr accuracy
The other interesting case to look at, would be when the other seven
outputs switch in the opposite direction to the one under test.
Some semiconductor data sheets specify that the specifications hold only
under very specific conditions, one of which may be that only one output
or input pin is switching, and the others are quiescent. Since IBIS
data sheets (models) don't have this as part of the specification, IBIS
models ought to cover all switching and loading combinations, right?? I
wonder how many IBIS models were created with that in mind. Probably
not many.
Regards,
Andy
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