RE: [IBIS-Users] IBIS [Add Submodel] workaround

Petar,

To remove the use of a Non-Driving Submodel for ODT, you can first
change the Model_Type to Input. Then delete all the output parameters
and keywords. And finally, add the Current data for the Model [GND
Clamp] to the Submodel [GND Clamp] and add the Model [POWER Clamp] to
the Submodel [POWER Clamp].

If the Voltage points do not match between the Model and the Submodel
curves, then the last step may not be straight forward. If your signals
do not reach the rails (this is likely the case if you are using ODT),
then as an approximation you should be able to simply replace the [GND
Clamp] and [POWER Clamp] data from the Model with that from the
Submodel. Although, depending on your data this may result in
non-monotonic curves.

Thanks,

Justin

P.S. If you are using one of Micron's models, contact me offline and we
may be able to modify one for you as an example.

From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On
Behalf Of Petar
Sent: Thursday, March 03, 2011 6:16 AM
To: ibis-users@eda.org
Subject: [IBIS-Users] IBIS [Add Submodel] workaround

 Hi,

I use EDA tool called Altium. It uses old version of ibis so every time
I want to do analysis I need to modify IBIS file for Altium to accept
it.

I know for a fact that Altium does not support [series_switch], [Add
Submodel] and [Model Selector]. I do not need to workaround
[series_switch], and i have managed to work around [Model Selector].

Now the last thing I need to do is to work around [Add Submodel]
keyword.

I'm simulating DDR3 memory modules, and I want to use their On Die
Terminations (ODT). Pin model looks like this:

[Model] DQ34_ODT20_1066
Model_type I/O
.
. some normal stuff from
. model definition here
.
[Add Submodel]
| Submodel Name Mode
20Ohm_ODT_1066 Non-Driving
|
[Temperature Range] 85.00 110.00 0.00
[Voltage Range] 1.500V 1.425V 1.575V
[Pullup Reference] 1.500V 1.425V 1.575V
[Pulldown]
.
. Pulldown table here
.
[Pullup]
.
. Pullup table here
.
[GND Clamp]
.
. GND Clamp table here
.
[POWER Clamp]
.
. POWER Clamp table here
.

After this are other model definitions, and my submodel is defined after
them:

.
.
[Submodel] 20Ohm_ODT_1066
Submodel_type Dynamic_clamp
|
|***********************************************************************
****
|
[GND Clamp]
|
.
. Submodel's GND Clamp table here
.
[POWER Clamp]
|
.
. Submodel's POWER Clamp table here
.

Since Altium does not support [Add Submodel], I can get correct results
for this pin only if I set it to output (driving). If it is set to Input
(Non-driving) a submodel should be used, and I will get wrong results.

Now, I want to modify this IBIS file by "implementing" data from
[Submodel] into [Model]. This way I would get correct results when doing
analysis with this pin set as input. I know that by doing that I will
not get correct results with this pin set as output, but that is OK. I
will then combine two IBIS files based on the analysis that I'm doing.

Do I have to simply replace [GND Clamp] and [POWER Clamp] tables from
the [Model] with the ones from the [Submodel], or do I have to use some
arithmetic functions in order to combine the two (or something third).

I hope I was clear, since I find this very hard to explain :-)

Regards
Petar Perisin

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