Subject: arbitrary length in ebd files?

From: "Kris Young" <[email-masked]>
Date: Fri, 13 Apr 2001 09:42:46 -0500

Hello:

I have a question about path descriptions in electronic board description
(ebd) files (IBIS 3.2).  I'm wondering how to get an accurate simulation of
signal reflections when the path length is given in terms of an arbitrary
length.  It seems like running an accurate SI simulation will require an
estimate as to what factor to scale the path lengths by to get them to match
the device specified by the ebd.  Why isn't there a way to specify a scale
factor in the ebd file?  Am I missing something?

Thanks in advance for your assistance.

Regards,

Kris Young
Phase IV Systems, Inc.
Huntsville, AL

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From: "Kris Young" <[email-masked]>
Date: Thu, 19 Apr 2001 17:01:41 -0500

I have one more question for the IBIS gurus out there.  I'm using Pspice to
model a signal path from an EBD file.  I've figured out everything except
what to do when the length is zero and there's an L and a C.  When I look at
the classic lumped lossy line (taking R=0 and G=inf), the series L comes
first and then the parallel C.  However, when I look at the classic lossless
case, the parallel C comes first, and then the series L.

Since the impedances of these configurations differ, which one should I use.
I can only guess, but it should be clearer than that, right?  Would the
lossy case be the one to use, even if there's no R?

Thanks again,

Kris Young

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From: Mike LaBonte <[email-masked]>
Date: Fri, 20 Apr 2001 06:39:20 -0400

Kris,

Why not use the PSPICE transmission line model? It is a true distributed
transmission line model, so you don't have to be concerned about how
to do the lumping. Also, it accepts per-length RLGC values. For example:

T3 one_end 0 other_end 0 LEN=1 C=3.1p L=1.05p

PSPICE accepts the notion that LEN is not in any particular units,
same as EBD. Of course you can add R= and G= for lossy lines, too.

That said, if you still need to create a lumped model, try splitting
the series elements in two to make it symmetric. For example, use
two inductors, each with half the inductance. This way a signal going
one way comes out identical to the same signal going the other way.
You can leave the middle series elements unsplit.

Mike LaBonte

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From: "Kris Young" <[email-masked]>
Date: Fri, 20 Apr 2001 09:34:04 -0500

Mike,

I have been using the PSPICE distributed transmission line model, and you're
right, it's very convenient to plug in the values from the EBD file.  I was
very relieved when I figured that out.

My question concerns the special case in the EBD file when LEN=0.
Supposedly this requires the use of a lumped element.  For instance, when
LEN=0 and R=0.003, it is specifying a series 3 mOhm resistor.  In the file
I'm simulating, there are a few cases where LEN=0, and L and C are
specified.  I'm trying to figure out what configuration of L and C is
specified by such a description.

Kris Young
Phase IV Systems, Inc.
Huntsville, AL

-----Original Message-----
From: Mike LaBonte [mailto:[email-masked]]
Sent: Friday, April 20, 2001 5:39 AM
To: Kris Young
Cc: [email-masked]
Subject: Re: another ebd modeling question

Kris,

Mike LaBonte

---

From: "Jongho Kang" <[email-masked]>
Date: Thu, 26 Apr 2001 16:55:21 +0900

Kris,

Did you figure out what configuration of L and C is used when Len=0 and
L and C is specified ?
I'm in the same situation as you was.  I'm trying to describe C-L-C lumped
circuit in the EBD.
If you figured out , please let me know.

Thanks,
Jongho Kang

----- Original Message ----- 
From: Kris Young <[email-masked]>
To: Mike LaBonte <[email-masked]>
Cc: <[email-masked]>
Sent: Friday, April 20, 2001 11:34 PM
Subject: RE: another ebd modeling question

Mike,

Kris Young
Phase IV Systems, Inc.
Huntsville, AL

-----Original Message-----
From: Mike LaBonte [mailto:[email-masked]]
Sent: Friday, April 20, 2001 5:39 AM
To: Kris Young
Cc: [email-masked]
Subject: Re: another ebd modeling question

Kris,

Mike LaBonte