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

From: Tom Dagostino <tom_at_.....>
Date: Thu Dec 18 2008 - 15:43:48 PST
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 Thu, 18 Dec 2008 15:43:48 -0800

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