[SI-LIST] Re: IBIS model Tr accuracy
- From: steve weir <weirsi@xxxxxxxxxx>
- To: Bradley.S.Henson@xxxxxxxxxx, <a.ingraham@xxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Wed, 19 Oct 2005 09:58:18 -0700
Brad, FAST wasn't the only offender then, and there have been many similar
offenders since. The sooner recent enhancements to IBIS that provide some
accounting of the PDS get into production models the better.
Regards,
Steve.
At 09:44 AM 10/19/2005 -0700, Henson, Bradley S wrote:
>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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