Subject: Re: Clarifing example for Packaging EGG

From: [email-masked] (Chrisopher E. Reid)
Date: Mon, 8 May 95 13:05:05 -0400

Hello,

I agree with Eric and Kumar. Spice syntax is the way to go
for package models because it is flexibile and sufficient.
Any circuit at all can be represented in SPICE.

The only thing we need to add is a standard syntax for
transmission lines and matricies, both of which I can propose
if there is interest in this direction.

We must also define a standard such as Kumar proposes on terminal
naming plus a convention that makes it easy for automatic software
to recognize mutual parasitics that can be edited out of the circuit
based on some coupling criteria (which is up to the software).

It is very important that Ibis support a broad, flexibile standard,
not a narrow and restricted one. It is also important to recognize
where the analysis software should do the work rather than the
modeler (such as removing small couplings).

Chris Reid

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From: [email-masked] (Richard A. Schumacher)
Date: Mon, 8 May 1995 12:48:19 -0500

J Eric Bracken <[email-masked]> writes:

  The one thing I _do_ worry about here is how the model MAKERS will 
go about producing the coupling information...using field solver software?
Doing cut-and-try on measured data?  With a dart board?  This could 
really affect the accuracy of results, particularly when different vendors
are doing their own thing.

	Aye, there's the rub. Package effects (crosstalk, ground/power
	bounce, etc.) often dominate or determine the device behavior, 
	so a discretionary approach to packages can make the models useless
	if the modeller is not careful. Drivers and receivers cannot be
	modelled correctly without their packaging, unless the packaging
	is so good that its effects are negligible. Maybe vendors should
	put more effort into making their packaging "invisible"... Until
	that happens, for IBIS to be useful it must include a prescription
	for package modelling.
	
	In my experience, the only useful models are based on measured 
	_AC_ data from actual parts. No 2-1/2D or 3D modeller I know of
	gives accurate results to useful precision in reasonable time,
	and quasi-DC I-V curves do not reveal package effects.

	Richard Schumacher