RE: [IBIS-Users] RE: [IBIS] C_comp value

From: NG,MEI-YEE <mei-yee.ng_at_.....>
Date: Mon Sep 29 2008 - 17:49:19 PDT
Dear Todd,

 

The netlist I used (..sp file) is a transistor-level netlist which was
extracted from the layout. Therefore, the netlist I used to create the
IBIS buffer should already have parasitic effects catered inside.

 

My question was more for the .s2i file. Inside this file, there's a
parameter [C_comp] that we have to include. If my netlist already has
the parasitic effects catered, do I still need to input the C_comp value
explicitly in the .s2i file?

 

Thank you. 

 

Best regards,

Mei Yee

MCPD, Avago Technologies (Malaysia)

Tel no.: +604-6108515

________________________________

From: owner-ibis-users@server.eda.org
[mailto:owner-ibis-users@server.eda.org] On Behalf Of Todd Westerhoff
Sent: Monday, September 29, 2008 8:59 PM
To: ibis-users@server.eda.org
Subject: Re: [IBIS-Users] RE: [IBIS] C_comp value

 

Mei-Yee,

Can you expand on the phrase "the netlist I used for the pad is an
extracted netlist"?

Do you mean the transistor-level netlist used to create the IBIS buffer
model in the first place ... that is, a transistor level netlist used to
perform simulation under controlled conditions, the results of which
were post-processed to create the IBIS buffer model?

If that's what you meant, and the transistor level netlist you started
with included the output buffer's capacitance, then the conversion
program (s2ibis3 or other) you used should have calculated and included
C_Comp automatically in your buffer model.   Arpad is correct that the
V-T curves in the IBIS model should include the effects of C_Comp, and
the IBIS simulator needs to combine the V-T data and C_Comp during
simulation without double-counting the effect of C_Comp.

... but I'm trying to understand whether your question was whether or
not C_Comp was to be added explicitly to the original transistor level
netlist.  The usual answer to that question is - no.

Todd.



Todd Westerhoff
VP, Software Products
SiSoft
6 Clock Tower Place, Suite 250
Maynard, MA 01754
(978) 461-0449 x24
twesterh@sisoft.com
www.sisoft.com



NG,MEI-YEE wrote: 

Hi Arpad,

 

Just one quick question, if the netlist I used for the pad is an
extracted netlist, does that mean the C_comp value is already
incorporated inside (parasitics and all)? In that case, if I still put
in an additional C_comp value, it would mean that I'm double-counting
the C_comp?

 

Thank you.

 

Best regards,

Mei Yee

MCPD, Avago Technologies (Malaysia)

Tel no.: +604-6108515

________________________________

From: owner-ibis-users@server.eda.org
[mailto:owner-ibis-users@server.eda.org] On Behalf Of Muranyi, Arpad
Sent: Friday, September 26, 2008 9:03 PM
To: ibis@server.eda.org
Cc: ibis-users@server.eda.org
Subject: [IBIS-Users] RE: [IBIS] C_comp value

 

Timmy,

 

You can do it either way, it depends on your needs.

If you want to correlate to your SPICE model, match

it to that, if you want to correlate to real life,

match it to your measurements.

 

Arpad

====================================================

 

________________________________

From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On
Behalf Of Timmy Leon
Sent: Thursday, September 25, 2008 8:46 PM
To: ibis@server.eda.org
Cc: ibis-users@server.eda.org
Subject: [IBIS] C_comp value

Dear Sir/Madam,

 

I have a question regarding the c_comp value that we should put in IBIS
model. Should the c_comp value be based on measurement, or can we tune
value so that IBIS model correlate with its spice model or measurements?
Thank you.

 

Best regards,

Timmy Leon



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Received on Mon Sep 29 17:52:55 2008

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