RE: [IBIS] How we can model startup time in IBIS.

From: Mandel, Cary <cary_mandel_at_.....>
Date: Mon May 14 2007 - 04:37:41 PDT
Hello Akhilesh,

There are two basic kinds of mismatch that you can have between spice
and IBIS simulation.

1) Waveforms are shifted in time, but shape of rising/falling edges
match. In this case, the IBIS simulator is probably doing the right
thing -- it is not the job of the IBIS model to model this "startup
time". 

2) Mismatch between the rising/falling edges in Spice as compared to the
IBIS simulator. You need to be careful when removing lead time in VT
curves. In many IBIS models, the relative delay between different VT
curves is very important. The safest thing to do is to remove the SAME
lead time from all curves for a particular driver model. This is the
safest thing to do. Optionally, there is a  refinement to this, which
is: a) For single ended models -- Remove the same lead time from all
RISING waveforms. Remove the same lead time for all FALLING waveforms;
b) For differential models --  The relative timing between RISING and
FALLING waveforms is important, so you should remove the same lead time
for all the RISING and FALLING waveforms.

Cary Mandel
Applications Engineer
Mentor Graphics

-----Original Message-----
From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On
Behalf Of Akhilesh CHANDRA
Sent: 14 May 2007 11:42
To: 'Itzhak Peleg'; ibis@server.eda-stds.org
Cc: Akhilesh CHANDRA
Subject: RE: [IBIS] How we can model startup time in IBIS.

Hello Itzik,

If I remove it from my VT table then I can run the design at 800MHZ but
then I have mismatch in IBIS and spice results. In this case my spice
have 3ns startup time but it's missing in IBIS models.

Regards
Akhilesh 

-----Original Message-----
From: Itzhak Peleg [mailto:itzikpe@marvell.com]
Sent: Monday, May 14, 2007 3:44 PM
To: Akhilesh CHANDRA; ibis@eda-stds.org
Subject: RE: [IBIS] How we can model startup time in IBIS.

Hi Akhliesh

You can you remove the same lead time in all curves.
For example removing 3ns from each curve subtracting the new 1st time
point from each time point (so the curve will start at 0ns time). Then
write the curves to the IBIS model.

--
Regards
 
Itzik Peleg
Board Technology Group
 
Marvell Semiconductor Israel Ltd
6 Hamada Street
Mordot HaCarmel Industrial Park
Yokneam 20692, ISRAEL
 
Email - itzikpe@marvell.com
Tel   - +972 4  9091192
Cell  - +972 54 4452482
Fax   - +972 4  9091501
WWW Page: http://www.marvell.com
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-----Original Message-----
From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On
Behalf Of Akhilesh CHANDRA
Sent: Monday, May 14, 2007 12:18 PM
To: ibis@server.eda-stds.org
Cc: Akhilesh CHANDRA
Subject: [IBIS] How we can model startup time in IBIS.

 

Hello Experts,

  I am doing IBIS model of an IO operating at 800MHZ frequency. It have
startup time of 3nsec. After 3ns design gives output of 800mhz
frequency. If I model this time in waveform database of IBIS models the
I have over clocking issue and design is not work at this high
frequency. Can you help me to model this startup time. Is anyone make
IBIS model of such designs.

Regards
Akhilesh


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Received on Mon May 14 04:38:11 2007

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