# [SI-LIST] : RE: arbitrary length in ebd files?

From: Dunbar, Tony ([email protected])
Date: Fri Apr 13 2001 - 08:22:46 PDT

Hi Kris,

It's not that intuitive, so don't feel bad for missing this.
The "scaling factor" is in the L and C values for the path.
If you look at the following (fairly well documented) example,
you can see/derive from the scale of the L and C values that
sqrt(LC) gives an answer of delay per unit length in s/m
(i.e. seconds per meter). But I also need the scale of the
L and C values to be correct to obtain the correct Zo=sqrt(L/C).
So I then use a Len value to specify the length of the segment.

In this example, one of segment my lengths needs to be 520mil
but I'm working in meters.

Hope this helps!

Regards,
Tony

[Path Description] XYZ
Pin B18
| 1. Path 1
Len = 0 L = 168.00e-12 C = 0.00 R = 0.006 /
| 2. Via
Len = 0 L = 570.00e-12 C = 0.00 R = 0.0021 /
| 3. Seg. #2 Use slow = 520mil, HighZ 50.3ohm.
Len = 0.013205 L = 3.591440e-07 C = 1.419672e-10 R = 6.931417e01 /
| 4. Seg. #1 Use slow = 80mil, HighZ 42.46ohm.
Len = 0.002032 L = 3.072277e-07 C = 1.704113e-10 R = 5.862795e01 /
| 5. Die bump
Len = 0 L = 20.00e-12 C = 0.0 R = 0.002 /
Node U1.B18

-----Original Message-----
From: Kris Young [mailto:[email protected]]
Sent: Friday, April 13, 2001 9:43 AM
To: [email protected]
Subject: arbitrary length in ebd files?

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?

Regards,

Kris Young
Phase IV Systems, Inc.
Huntsville, AL

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