From: owner-ibis-users@eda.org (ibis-users) To: ibis-users-digest@eda.org Subject: ibis-users V1 #237 Reply-To: Sender: owner-ibis-users@eda.org Errors-To: owner-ibis-users@eda.org Precedence: bulk ibis-users Monday, July 14 2014 Volume 01 : Number 237 ---------------------------------------------------------------------- Date: Wed, 11 Jun 2014 06:39:05 +0000 From: Saravanan Ganesh Subject: RE: [IBIS-Users] full differential buffer IBIS modeling ---clarification - --_000_3BCB40031507A5489A4F9DCBF414F27A407E1BDCONWATER51Madons_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi Using =BD of R_diff to ground and simulating the V-T char dos not settle th= e outputs at required levels. actually according to the termination as shown in attachment the rl =3D50o= hm connected from each differential output to common cap and cap is connec= ted to Vcm_rx w .r.t gnd. How to divide this in to half? And get ibis model correct? What values to be used in the Rfixture , vfixture, Rref ,Vref, Vmeas ,etc= in .s2i file Regards Saravanan.G From: Lynne Green [mailto:lgreen22@mindspring.com] Sent: Friday, May 09, 2014 10:39 PM To: Saravanan Ganesh; ibis-users@eda.org Subject: Re: [IBIS-Users] full differential buffer IBIS modeling ---clarifi= cation Dear Saravanan, A differential buffer in IBIS 3.2 requires two buffer models, one for each = output. To use s2ibis3: - -Use the SAME load to ground for EACH output. - - Do not use a differential resistor between the two outputs. Use 1/2 of R= _diff to ground. - - Run s2ibis3 once, using the inverting output pin, and create BUFFER1. Ru= n it again for the non-inverting output pin, and create BUFFER2. Note that= no other changes are made between the two runs. - - In the models, be sure to label the output type to indicate BUFFER1 is in= verting and BUFFER2 is non-inverting. For simulation, assign BUFFER1 to the inverting pin and BUFFER2 to the non-= inverting pin. Under [Diff Pin], list the buffers with ZERO time offset (t= he time offset is captured in the V-t tables). At least one simulation, wi= th R=3DRload, should be used to test the model before releasing it for use,= another with a different R is recommended.. Hope this helps. PS: if you plan do this often, you can modify the s2ibis3 source to capture= both outputs in just one run of s3ibis3. Not sure why no-one has shared t= heir modification with the IBIS Open Forum. Cheers, Lynne Green retired On 5/9/2014 8:20 AM, Lance Wang wrote: Saravanan, The first, s2ibis3 can be used for simple single-end buffer only. It might = not be satisfied for differential buffers. The second, R_load in s2i is the same as R_fixture in the IBIS file. The third, full/true differential pair buffer IBIS extraction will not be h= andled by s2ibis3 correctly. Another word, you will never be able to get co= rrect IBIS models thru s2ibis3 for your full differential buffers. Hope this helps. Lance Wang IO Methodology Inc. 978-266-8981 SimDE MODEL, the best IBIS modeling tool in the market. http://www.iometh.com From: Saravanan Ganesh > Date: Friday, May 9, 2014 at 9:55 AM To: "ibis-users@eda.org" > Subject: [IBIS-Users] full differential buffer IBIS modeling ---clarificati= on Hi I want to brief on the R_load I am using I am creating IBIS model (Version 3.2) of a full differential buffer . I have also connected the termination shown in "diffbuff_termination.png" = in differential buffer schematic. Even though I have connected the required termination in schematic itself ,= the .s2i file need R_load value to be supplied. Therefore I have used a High value resistor (R_load=3D100G ohm) in .s2i fil= e. Hyperlinx "Check file for IBIS spec conformance" gives following error ... ERROR: Model OUTPUT_DIF: The [Rising Waveform] with [R_fixture]=3D1e+011 Ohms and [V_fixture_max]=3D0.22V has MAX column DC endpoints of 0.08V and 0.31v, but an equivalent load applied to the model's I-V tables yields different voltages ( 0.08V and 0.35V), a difference of 0.01% and 16.09%, respectively. What could be wrong? What can I do to get rid of these errors and warnings? Please mail me if any more clarification required ,Waiting for your replies. Thanks and regards Saravanan.G From: Saravanan Ganesh Sent: Thursday, May 08, 2014 8:04 PM To: 'ibis-users@eda.org' Subject: full differential buffer IBIS modeling Hi I am creating IBIS model (Version 3.2) of a full differential buffer . I have also connected the termination shown in "diffbuff_termination.png" = in differential buffer schematic. Therefore I took R_load =3D 100G ohm in = .s2i file, so that only load in schematic are effective. Hyperlinx "Check file for IBIS spec conformance" gives following error ... ERROR: Model OUTPUT_DIF: The [Rising Waveform] with [R_fixture]=3D1e+011 Ohms and [V_fixture_max]=3D0.22V has MAX column DC endpoints of 0.08V and 0.31v, but an equivalent load applied to the model's I-V tables yields different voltages ( 0.08V and 0.35V), a difference of 0.01% and 16.09%, respectively. What could be wrong? What can I do to get rid of these errors and warnings? Thanks and regards Saravanan.G - -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. - -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. - --=20 This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. - --_000_3BCB40031507A5489A4F9DCBF414F27A407E1BDCONWATER51Madons_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Hi

Using =BD of R_diff to= ground and simulating the V-T char dos not settle the outputs at required = levels.

actually according to = the termination as shown  in attachment the rl =3D50ohm connected from= each differential output  to common cap and cap is connected to Vcm_r= x w .r.t  gnd.

How to divide this in = to half? And get ibis model correct?

What values  to b= e used in the Rfixture , vfixture,  Rref ,Vref, Vmeas ,etc in .s2i file

Regards

Saravanan.G=

 

 

From: Lynne Green [mailto:lgreen22@mindspring.com]
Sent: Friday, May 09, 2014 10:39 PM
To: Saravanan Ganesh; ibis-users@eda.org
Subject: Re: [IBIS-Users] full differential buffer IBIS modeling ---= clarification

 

Dear Saravanan,

A differential buffer in IBIS 3.2 requires two buffer models, one for each = output.

To use s2ibis3:
- -Use the SAME load to ground for EACH output. 
- - Do not use a differential resistor between the two outputs.  Use 1/2= of R_diff to ground.
- - Run s2ibis3 once, using the inverting output pin, and create BUFFER1.&nbs= p; Run it again for the non-inverting output pin, and create BUFFER2. = Note that no other changes are made between the two runs.
- - In the models, be sure to label the output type to indicate BUFFER1 is in= verting and BUFFER2 is non-inverting. 

For simulation, assign BUFFER1 to the inverting pin and BUFFER2 to the non-= inverting pin.  Under [Diff Pin], list the buffers with ZERO time offs= et (the time offset is captured in the V-t tables).  At least one simu= lation, with R=3DRload, should be used to test the model before releasing it for use, another with a different R is recom= mended..

Hope this helps.

PS: if you plan do this often, you can modify the s2ibis3 source to capture= both outputs in just one run of s3ibis3.  Not sure why no-one has sha= red their modification with the IBIS Open Forum.

Cheers,
Lynne Green
retired


On 5/9/2014 8:20 AM, Lance Wang wrote:

Saravanan,

The first, s2ibis3 can be used for simple single-end= buffer only. It might not be satisfied for differential buffers.

 

The second, R_load in s2i is the same as R_fixture i= n the IBIS file. 

 

The third, full/true differential pair buffer IBIS e= xtraction will not be handled by s2ibis3 correctly. Another word, you will = never be able to get correct IBIS models thru s2ibis3 for your full differe= ntial buffers.

 

Hope this helps.

 

Lance Wang

IO Methodology Inc.

978-266-8981

 

SimDE MODEL, the best IBIS modeling tool in the mark= et.

 

 

 

 

 

From: Saravanan Ganesh <Saravanan.Ganesh@onsemi.com>
Date: Friday, May 9, 2014 at 9:55 AM
To: "ibis-users@eda.org" <ibis-users@eda.org&g= t;
Subject: [IBIS-Users] full differential buffer IBIS modeling ---clar= ification

 

Hi <= /p>

I want to  brief = on the R_load  I am using

 

I am creating  IBIS model (Version 3.2) of a fu= ll differential buffer .

I have also  connected the termination shown in= “diffbuff_termination.png” in differential buffer schematic.

 

Even though I have con= nected the required termination in schematic itself , the .s2i file need R_= load value to be supplied.

Therefore I have used = a High value resistor (R_load=3D100G ohm) in .s2i file.

 

Hyperlinx “Check file for IBIS spec conformanc= e”  gives following  error …

 

ERROR: Model OUTPUT_DIF: The [Rising Waveform] =

      with [R_fixture]= =3D1e+011 Ohms and [V_fixture_max]=3D0.22V

      has MAX column DC end= points of  0.08V and  0.31v, but

      an equivalent load ap= plied to the model's I-V tables yields

      different voltages ( = 0.08V and  0.35V),

      a difference of = 0.01% and 16.09%, respectively.

 

W= hat could be wrong? What can I do to get rid of these errors and warnings?<= /span>

&= nbsp;

P= lease mail me if any more clarification required ,Waiting for your replies.

T= hanks and regards

S= aravanan.G

 

 

From: Saravana= n Ganesh
Sent: Thursday, May 08, 2014 8:04 PM
To: 'ibis-users@eda.org= '
Subject: full differential buffer IBIS modeling

 

Hi

I am creating  IBIS model (Version 3.2) of a fu= ll differential buffer .

I have also  connected the termination shown in= “diffbuff_termination.png” in differential buffer schematic. T= herefore  I took R_load =3D 100G ohm in .s2i file, so that only load i= n schematic are effective.

Hyperlinx “Check file for IBIS spec conformanc= e”  gives following  error …

 

ERROR: Model OUTPUT_DIF: The [Rising Waveform] =

      with [R_fixture]= =3D1e+011 Ohms and [V_fixture_max]=3D0.22V

      has MAX column DC end= points of  0.08V and  0.31v, but

      an equivalent load ap= plied to the model's I-V tables yields

      different voltages ( = 0.08V and  0.35V),

      a difference of = 0.01% and 16.09%, respectively.

 

W= hat could be wrong? What can I do to get rid of these errors and warnings?<= /span>

&= nbsp;

T= hanks and regards

S= aravanan.G


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This message has been scanned for viruses and
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This message has been scanned for viruses and
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--=20
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean. - --_000_3BCB40031507A5489A4F9DCBF414F27A407E1BDCONWATER51Madons_-- - -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail mikelabonte@eda-stds.org |or ibis-request@eda-stds.org | |IBIS reflector archives exist under: | | http://www.eda-stds.org/ibis/email_archive/ Recent | http://www.eda-stds.org/ibis/users_archive/ Recent | http://www.eda-stds.org/ibis/email/ E-mail since 1993 ------------------------------ Date: Mon, 14 Jul 2014 16:15:02 +0000 From: "Muranyi, Arpad" Subject: RE: [IBIS-Users] A question on how to handle NA in the min/max columns Bob, Thanks for your response, but remember, I am asking this as an EDA vendor. And a big aspect of my question is what the EDA tool is expected to do with such models. The spec is quite vague, and I think it should define a few rules. We can't just throw out all models and abort the simulation if we find NA-s in the min/max corner in any of the keywords for which the spec doesn't say to use the typ value when min/max is not available. But this also applies to the model makers. The spec should have a few rules on what keyword combinations can have NA in the min/max columns. The way the spec goes now, a lot of combinations are allowed which do not make sense or can't be simulated. Thanks, Arpad ================================================================= - -----Original Message----- From: Bob Ross [mailto:bob@teraspeed.com] Sent: Friday, July 11, 2014 8:59 PM To: Muranyi, Arpad; 'IBIS-users' Subject: RE: [IBIS-Users] A question on how to handle NA in the min/max columns Arpad: You have provided a good analysis and scratched the surface of the problem. I do not think IBIS should make it illegal to have some, but not all corner data missing (e.g. the min and max columns for some tables are NA). There are pathological cases where such a models are still accurate and useful. E.g, ideal 50 ohm source resistors for the pullup and pulldown tables to the defined pulldown and pullup reference voltages for all corners with only the typ table is given and the min/max table corners have NA entries. The intent might be to model a fixed 50 ohm impedance for all pullup and pulldown table corners and vary the V-T data.) Or just providing an ideal 50 ohm termination for all corners could be done with just the typical data only, and that can be used with other models with all numerical corner data given. However, the user should be suspicious of and probably reject models for real buffers with NAs in the corners because they are incomplete or contain uncorrelated information that would make corner analysis inaccurate. Bob - -----Original Message----- From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf Of Muranyi, Arpad Sent: Friday, July 11, 2014 10:45 AM To: IBIS-users Subject: [IBIS-Users] A question on how to handle NA in the min/max columns Hello, I would like to discuss the question of how to handle the situations when min/max data is not available in certain IBIS keywords. The IBIS specification has several occurrences of the following statement (with some variations here and there): If minimum and/or maximum values are not available, the reserved word "NA" must be used indicating the typical value by default. (This one can be found on pg. 36 at the end of the 1st paragraph of the Usage Rules on the top of the page). The interesting thing is that this statement does not appear under every single keyword, so my first question is whether this was intentional or sloppiness. For example, pg. 53 where the I-V tables are described, we can read the following: All four columns are required under these keywords. However, data is only required in the typical column. If minimum and/or maximum current values are not available, the reserved word "NA" must be used. "NA" can be used for currents in the typical column, but numeric values MUST be specified for the first and last voltage points on any I-V table. Each I-V table must have at least 2, but not more than 100, rows. This section does not state what the EDA tool should do when min/max data is not available. My guess is that the expectation was that the EDA tool should use the typical data, but this is not stated. The same observation can also be made for the waveform tables on pg. 69, [Composite Current] on pg. 71/72 and the [ISSO ***] keywords on pg. 56. The story gets more interesting when we consider how the I-V tables and the waveform voltages are related to each other by Ohm's law using the R_fixture load resistor value. One might argue that if the min/max data is missing from the waveform tables, the typical waveform data might be "adjusted" (scaled) relatively easily so that they would be in agreement by Ohm's law. One could even do the reverse when the min/max data is available in the waveform tables but are missing in the I-V tables. But things will get more complicated or perhaps impossible with the [ISSO ***] and/or [Composite Current] tables. Imagine a certain waveform which includes typ/min/max, but the [Composite Current] following it has only typ data (or the other way around). So the question I would like to clarify is whether the IBIS specification should define what to do in these cases, or perhaps impose some requirements on how the model maker should provide the data for these various keywords (i.e. require all of them to have or not have min/max data). Note that not all keywords fall into this category. For example, C_comp and its variants are relatively independent from I-V and waveform related keywords, so these would not have to be "matched" with having or not having min/max data. Questions, comments welcome... Thanks, Arpad ============================================================================ == - -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. - -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail mikelabonte@eda-stds.org |or ibis-request@eda-stds.org | |IBIS reflector archives exist under: | | http://www.eda-stds.org/ibis/email_archive/ Recent | http://www.eda-stds.org/ibis/users_archive/ Recent | http://www.eda-stds.org/ibis/email/ E-mail since 1993 - -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. - -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail mikelabonte@eda-stds.org |or ibis-request@eda-stds.org | |IBIS reflector archives exist under: | | http://www.eda-stds.org/ibis/email_archive/ Recent | http://www.eda-stds.org/ibis/users_archive/ Recent | http://www.eda-stds.org/ibis/email/ E-mail since 1993 ------------------------------ End of ibis-users V1 #237 *************************