[SI-LIST] FW: Re: What frequency are IBIS models good to?
- From: "Muranyi, Arpad" <arpad.muranyi@xxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Mon, 20 Sep 2004 11:32:35 -0700
With the permission of Fred from Apsimtech, I would
like to post his comments he sent me privately on the
list.
Arpad
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=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
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-----Original Message-----
From: Fred Balistreri
Sent: Wednesday, September 15, 2004 4:44 PM
To: Muranyi, Arpad
Subject: Re: [SI-LIST] Re: What frequency are IBIS models good to?
Just a comment. Although some SPICE do or did have limitations with
equations I don't think that was a reason for using PWL. Most SI =
simulation
engines of that era were not SPICE based. Quad comes to mind. That was
very popular and they had a lot to say in those days. Interconnectix was
another such SI tool as well as Hyperlynx.
Anyway my point is the simulation vendors of the time were not SPICE
based and that is what drove the PWL spec as much as anything else.
Best Regards,
Fred
----- Original Message -----=20
From: "Muranyi, Arpad" <arpad.muranyi@xxxxxxxxx>
To: "si-list" <si-list@xxxxxxxxxxxxx>
Sent: Wednesday, September 15, 2004 4:22 PM
Subject: [SI-LIST] Re: What frequency are IBIS models good to?
> VS,
>
> Excellent comments. Here are a few more...
>
> 1) Thanks.
>
> 2) Depending on who you ask, it can go well beyond 1 GHz.
> I don't think there is a specific hard limit that
> anyone can set. It is similar (but even less
> definable in my opinion) to the question, how far=3D20
> up can we use FR4?
>
> 3-4) Good point, and I have been talking about this for
> years. The points can be fitted to an equation which
> would probably be even faster than the PWL approach
> plus it could be scaled instead of having three
> distinct corners (typ., min., max).
>
> The reason we started IBIS with the table format
> is because we used exactly what you say, controlled=3D20
> sources in SPICE. It was easier to use the PWL
> sources with lab measured data, which is what we
> did in many cases. We just got stuck with that
> format in IBIS, but now you can do it through the
> *-AMS extensions of the spec any whichever way you
> please.
>
> Part of the problem with using SPICE was (is) that
> its equation capabilities was (is) quite limited
> (depending on which flavor you have).
>
> 5-6) The original question was asking about IBIS being
> nothing but DC IV curves, so I assumed that the
> person asking this was talking about buffers only.
> That's why I didn't bring in the package and EBD
> aspects of IBIS, which I agree are quite limited.
>
> If you need anything decent on that front fro high
> frequency simulations, consider the (new) ICM
> specification. It provides much more capabilities
> and accuracy in many areas, including the ones you
> mentioned (coupling, etc...).
>
> It is a new spec, so there are not too many models
> available yet, but just this week's HSPICE release does
> have support for it, so we can now all start using it...
>
> 7) The reasons were IP, simulation speed, and the relative
> ease of doing "what if" analysis by manipulating the IV
> curves instead of the transistor level circuit design
> and/or its process parameters. We could also add in tool
> independence, and lack of SPICE models.
>
> Sorry for my ignorance, but could you please clarify
> what you meant by Linux-way, instead of Microsoft-way?
> I don't see the connection there.
>
> I am not sure if you mean the same, but if we had better
> equation and behavioral modeling capability in most flavors
> of SPICE (not just HSPICE), we would have probably never
> started IBIS...
>
> 8) You are absolutely right. But IBIS became a standard for
> different reasons. Probably mostly to have a common
> format that everyone could use, independently from which
> vendor's tool they use in their work.
>
> 9) That capability was there for a long time in the B-element
> of HSPICE. They provide scaling coefficients for various
> purposes. Unfortunately these are not features of legacy
> IBIS, but now we could do it with the *-AMS extensions of
> IBIS.
>
> Thanks,
>
> Arpad
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