RE: [IBIS-Users] IV/VT mismatch warnings with all corners file; no warnings with a single corner file

From: Anand Ramalingam <anandr_at_.....>
Date: Fri Dec 19 2008 - 15:05:54 PST
Hi Tom and Experts,

 

I had attached the ibis files in a *.tar.gz file. I am reattaching the
same tar.gz file which contains all the ibis files. I looked at my spice
files to see if they differed in signal settings for IV/VT extraction
(after Tom's suggestion). They don't differ.

 

My concern is why the warnings show up in the all corner ibis file
(all.ibs) when it doesn't show up in the single corner file (ss*.ibs)
when in fact the data looks identical (at least for the Pulldown case).

 

Thanks once again

Anand

 

________________________________

From: Tom Dagostino [mailto:tom@teraspeed.com] 
Sent: Thursday, December 18, 2008 5:44 PM
To: Anand Ramalingam; ibis-users@eda.org
Subject: RE: [IBIS-Users] IV/VT mismatch warnings with all corners file;
no warnings with a single corner file

 

Anand

 

From the data presented (the IBIS files do not come through as
attachments) you seem to have a weak pullup (0.4 mA) in the model that
is present in the IV curves but was not present when the VT curves were
extracted.  Re-extract the VTs with the pullup.

 

Tom Dagostino
Teraspeed(R) Labs
13610 SW Harness Lane
Beaverton, OR 97008
503-430-1065

503-430-1285 FAX
tom@teraspeed.com
www.teraspeed.com

Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
401-284-1827 

 

From: owner-ibis-users@server.eda.org
[mailto:owner-ibis-users@server.eda.org] On Behalf Of Anand Ramalingam
Sent: Thursday, December 18, 2008 3:14 PM
To: ibis-users@server.eda.org
Subject: [IBIS-Users] IV/VT mismatch warnings with all corners filie; no
warnings with a single corner file

 

Hi IBIS Experts,

 

I am trying to figure out why ibischk gives warnings about IV/VT
mismtach when I have all the corners in the IBIS file while it passes
without any errors or warnings for a single corner file.

 

I am attaching the 3 single corner files (ff_1p32_1p95_m40c.ibs;
ss_1p08_1p65_125c.ibs;  tt_1p10_1p80_25c.ibs) and one all corner file
(all.ibs).

 

When I run a ibischk on all.ibs, I get the following:

 

*------------------------------------------------------

IBISCHK4 V4.1.1

 

Checking all.ibs for IBIS 4.1 Compatibility...

--- first 5 warnings (not related to iv/vt mismatch) deleted ---

 

WARNING - Model MPADN: The [Rising Waveform] 

      with [R_fixture]=50 Ohms and [V_fixture_min]=0V

      has MIN column DC endpoints of  0.00V and  0.32v, but

      an equivalent load applied to the model's I-V tables yields

      different voltages ( 0.02V and  0.34V),

      a difference of  6.05% and  6.95%, respectively.

WARNING - Model MPADN: The [Falling Waveform] 

      with [R_fixture]=50 Ohms and [V_fixture_min]=0V

      has MIN column DC endpoints of  0.00V and  0.32v, but

      an equivalent load applied to the model's I-V tables yields

      different voltages ( 0.02V and  0.34V),

      a difference of  6.05% and  6.95%, respectively.

WARNING - Model MPADP: The [Rising Waveform] 

      with [R_fixture]=50 Ohms and [V_fixture_min]=0V

      has MIN column DC endpoints of  0.00V and  0.32v, but

      an equivalent load applied to the model's I-V tables yields

      different voltages ( 0.02V and  0.34V),

      a difference of  6.05% and  6.95%, respectively.

WARNING - Model MPADP: The [Falling Waveform] 

      with [R_fixture]=50 Ohms and [V_fixture_min]=0V

      has MIN column DC endpoints of  0.00V and  0.32v, but

      an equivalent load applied to the model's I-V tables yields

      different voltages ( 0.02V and  0.34V),

      a difference of  6.05% and  6.95%, respectively.

 

Errors  : 0

Warnings: 9

*------------------------------------------------------------------

 

 

I did check manually the Pulldown/Clamp data in single corner file
(ss_1p08_1p65_125c.ibs) and the one in min corner of all corner
(all.ibs) file. They look identical. 

 

I am little puzzled by why there warnings in all.ibs file while none
shows up in ss_1p08_1p65_125c.ibs file. I would be glad if someone can
help me understand why this warnings show up!

 

Thanks

Anand


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Received on Fri Dec 19 15:08:37 2008

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