**From:** Dunbar, Tony (*tony_dunbar@mentorg.com*)

**Date:** Fri Apr 13 2001 - 08:22:46 PDT

**Next message:**J. Eric Bracken: "[SI-LIST] : IBIS model for ECL gate?"**Previous message:**Ritchey Lee: "Re: [SI-LIST] : Diff clocks length matching"

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:kyoung@phaseiv.com]

Sent: Friday, April 13, 2001 9:43 AM

To: ibis-users@eda.org

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?

Thanks in advance for your assistance.

Regards,

Kris Young

Phase IV Systems, Inc.

Huntsville, AL

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**Next message:**J. Eric Bracken: "[SI-LIST] : IBIS model for ECL gate?"**Previous message:**Ritchey Lee: "Re: [SI-LIST] : Diff clocks length matching"

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