Thanks for the message. The major issue appe= ars to be=20 problems in generating the Vcc-relative information, but some general suppl= y=20 issues are cropping up too. Assu= ming this is=20 just a regular I/O buffer without internal terminations...

1) I would expect the Pullup I-V tables to pass th= rough the=20 zero V, zero I axis intercept. Yet they do not, with the max and min = data=20 shifted by ~0.3 V above and below 0 V, respectively. This suggests th= at=20 the math used to generate the tables may be incorrect. Remember=20 that, if the data at Vout is collected ground-relative, you can make t= he=20 power clamp and pullup table data in Vcc-relative by the formula (Vtable_co= rner=20 =3D Vcc_corner - Vout_corner), where xxx_corner refers to a value collected= for=20 typ, min or max. For example, if Vcc_min is 4.5 V, data collecte= d=20 ground-relative for 0.0 at the output would be entered in the table fo= r the=20 4.5 V row.

The supply voltages and the Pullup I-V axis interc= epts=20 (when plotted ground-relative) don't agree, which implies a problem with th= e=20 supply listed for the [Voltage Range] keyword not matching either the = real=20 circuit or the values used to generate the Vcc-relative=20 tables.

2) The voltage for the buffer is 5 V +/- 0.5, but = the V-t=20 fixture is 3.3 V +/- 0.3 V. This complicates the math (it gets very h= ard=20 for me to calculate the intercepts if they don't match, at least before my = first=20 cup of coffee), but it also suggests that the buffer V-t and I-V data sets = were=20 collected using different settings or otherwise using different=20 conditions. I would recommend checking the actual fixtures used for t= he=20 V-t extraction; matching the fixture voltages to the voltage supply would m= ake=20 checking easier.

Calculating the right I-V intercepts vs. V-t level= s will be=20 easier once these issues are addressed.

- Michael Mirmak

Intel Corp.

Chair, EIA IBIS Open Forum

From: owner-ibis@server.eda.org=20 [mailto:owner-ibis@server.eda.org] On Behalf Of Sudarshan H=20 N
Sent: Thursday, October 18, 2007 2:16 AM
To:=20 ibis@server.eda.org; ibis-users@server.eda.org
Subject: [IBIS] I-= V and=20 V-t curve mismatch

Hello Experts,

I am finding problem with one of my IBIS m= odel=20 in I-V and V-t curve mismatch. Please find the attached model for the=20 refernence.

ERROR - Model dummy: The [Rising=20 Waveform]
      with [R_fixture]=3D80 Ohms and= =20 [V_fixture]=3D0V
      has TYP column DC endpoi= nts=20 of 0.01V and 2.66v, but
      an=20 equivalent load applied to the model's I-V tables=20 yields
      different voltages (-0.00V and&nbs= p;=20 3.90V),
      a difference of 0.25% and= =20 31.85%, respectively.

I wrote a new tool to generate IBIS models and= i am=20 not able to make out where it is going wrong.
I actually tried to manual= ly=20 calculate the currents at the points , that it has reported in the above=20 error.

As it is a rising waveform having a R_fixture to ground = the=20 current at 2.66v (steady state) would be 2.66v/50 =3D 33.25mA.

I loo= ked at=20 the voltage corresponding to 33.25mA in pullup table and i found it is comi= ng=20 around 0.66v. There is a mismatch in the way i am caluculating also. But i= =20 observed a different voltage of 0.66v compared to what ibischk4 has reporte= d=20 i.e, 3.9v.

Let me know is the way i am cross checking is correct or= not=20 ? If not let me know the exact procedure.

Also let me know wha= t=20 might have been gone wrong in the curves. From the shape of the curves i am= not=20 seeing any problem with the way i have generated.

Please let me kno= w=20 your answers as soon as possible.

Note : Please dont consider any ot= her=20 values apart from the curves like Ramp , C_comp etc as i have dummy values = for=20 these place holders.

Thanks & Regards
Sudarshan

--=20
This message has been scanned for viruses and
dangerous content by = MailScanner, and is
be= lieved=20 to be clean.
--=20
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean. - ------_=_NextPart_001_01C8119F.C8FA237B-- - -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail majordomo@eda-stds.org |with the appropriate command message(s) in the body: | | help | subscribe ibis | subscribe ibis-users | unsubscribe ibis | unsubscribe ibis-users | |or e-mail a request to ibis-request@eda-stds.org. | |IBIS reflector archives exist under: | | http://www.eda-stds.org/pub/ibis/email_archive/ Recent | http://www.eda-stds.org/pub/ibis/users_archive/ Recent | http://www.eda-stds.org/pub/ibis/email/ E-mail since 1993 ------------------------------ Date: Fri, 19 Oct 2007 11:02:08 +0530 From: "Sudarshan H N" Subject: [IBIS-Users] Re: [IBIS] I-V and V-t curve mismatch - ------=_Part_4972_15517274.1192771928040 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline Hi Michael, Thanks for your detailed reponse. I made a small mistake in putting the voltage ranges as you mentioned. As i was writing a new tool , at this point of time i didnt give much attention to printing correct voltage range , and i was only worried about the correct extraction of V-t and I-V tables. I have considered the formula you have mentioned for calculating Vcc-relative Pullup and Powerclamp tables. I changed the voltage range to ( 3.3, 3.0 and 3.6 which is the actual case) and now i am able to get rid of all these errors. But still i have one query regarding the values for I-V curves when it is in the Min or MAX corner. I asked about this in my previous mail. Lynne and Arpad gave some answers but that didnt solve my problem. The problem with MIN and MAX corner is , what is the voltage range we need to consider for MIN and MAX case . For example if we consider 3.3 V supply, the typical range would be -3.3 to 6.6 and this is the voltage range in the IBIS file for all 3 corners. As per the cookbook we need to consider voltage range -Vcc to +2Vcc and hence for the MIN case the range will be -3.0 to +6.0. So in that case what current values we need to put for the voltage range -3.3 to -3.0 and +6.0 to +6.6 whose values will be missing in MIN corner simulations. I hope i have explained the problem correctly and let me know your answers. Thanks & Regards Sudarshan On 10/18/07, Mirmak, Michael wrote: > > Sudarshan, > > Thanks for the message. The major issue appears to be problems in > generating the Vcc-relative information, but some general supply issues are > cropping up too. Assuming this is just a regular I/O buffer without > internal terminations... > > 1) I would expect the Pullup I-V tables to pass through the zero V, zero I > axis intercept. Yet they do not, with the max and min data shifted by ~0.3 > V above and below 0 V, respectively. This suggests that the math used to > generate the tables may be incorrect. Remember that, if the data at Vout is > collected ground-relative, you can make the power clamp and pullup table > data in Vcc-relative by the formula (Vtable_corner = Vcc_corner - > Vout_corner), where xxx_corner refers to a value collected for typ, min or > max. For example, if Vcc_min is 4.5 V, data collected ground-relative for > 0.0 at the output would be entered in the table for the 4.5 V row. > > The supply voltages and the Pullup I-V axis intercepts (when plotted > ground-relative) don't agree, which implies a problem with the supply > listed for the [Voltage Range] keyword not matching either the real circuit > or the values used to generate the Vcc-relative tables. > > 2) The voltage for the buffer is 5 V +/- 0.5, but the V-t fixture is 3.3 V > +/- 0.3 V. This complicates the math (it gets very hard for me to > calculate the intercepts if they don't match, at least before my first cup > of coffee), but it also suggests that the buffer V-t and I-V data sets were > collected using different settings or otherwise using different conditions. > I would recommend checking the actual fixtures used for the V-t extraction; > matching the fixture voltages to the voltage supply would make checking > easier. > > Calculating the right I-V intercepts vs. V-t levels will be easier once > these issues are addressed. > > - Michael Mirmak > Intel Corp. > Chair, EIA IBIS Open Forum > > ------------------------------ > *From:* owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] *On > Behalf Of *Sudarshan H N > *Sent:* Thursday, October 18, 2007 2:16 AM > *To:* ibis@server.eda.org; ibis-users@server.eda.org > *Subject:* [IBIS] I-V and V-t curve mismatch > > Hello Experts, > > I am finding problem with one of my IBIS model in I-V and V-t curve > mismatch. Please find the attached model for the refernence. > > ERROR - Model dummy: The [Rising Waveform] > with [R_fixture]=80 Ohms and [V_fixture]=0V > has TYP column DC endpoints of 0.01V and 2.66v, but > an equivalent load applied to the model's I-V tables yields > different voltages (-0.00V and 3.90V), > a difference of 0.25% and 31.85%, respectively. > > I wrote a new tool to generate IBIS models and i am not able to make out > where it is going wrong. > I actually tried to manually calculate the currents at the points , that > it has reported in the above error. > > As it is a rising waveform having a R_fixture to ground the current at > 2.66v (steady state) would be 2.66v/50 = 33.25mA. > > I looked at the voltage corresponding to 33.25mA in pullup table and i > found it is coming around 0.66v. There is a mismatch in the way i am > caluculating also. But i observed a different voltage of 0.66v compared to > what ibischk4 has reported i.e, 3.9v. > > Let me know is the way i am cross checking is correct or not ? If not let > me know the exact procedure. > > Also let me know what might have been gone wrong in the curves. From the > shape of the curves i am not seeing any problem with the way i have > generated. > > Please let me know your answers as soon as possible. > > Note : Please dont consider any other values apart from the curves like > Ramp , C_comp etc as i have dummy values for these place holders. > > Thanks & Regards > Sudarshan > > > > -- > 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. - ------=_Part_4972_15517274.1192771928040 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline Hi Michael,

Thanks for your detailed reponse. I made a small mistake in putting the voltage ranges as you mentioned. As i was writing a new tool , at this point of time i didnt give much attention to printing correct voltage range , and i was only worried about the correct extraction of V-t and I-V tables.

I have considered the formula you have mentioned for calculating Vcc-relative Pullup and Powerclamp tables. I changed the voltage range to (3.3, 3.0 and 3.6 which is the actual case) and now i am able to get rid of all these errors.

But still i have one query regarding the values for I-V curves when it is in the Min or MAX corner. I asked about this in my previous mail. Lynne and Arpad gave some answers but that didnt solve my problem.

The problem with MIN and MAX corner is , what is the voltage range we need to consider for MIN and MAX case . For example if we consider 3.3 V supply, the typical range would be -3.3 to 6.6 and this is the voltage range in the IBIS file for all 3 corners. As per the cookbook we need to consider voltage range -Vcc to +2Vcc and hence for the MIN case the range will be -3.0 to +6.0. So in that case what current values we need to put for the voltage range -3.3 to -3.0 and +6.0 to +6.6 whose values will be missing in MIN corner simulations.

I hope i have explained the problem correctly and let me know your answers.

Thanks & Regards
Sudarshan

On 10/18/07, Mirmak, Michael <michael.mirmak@intel.com> wrote:

Sudarshan,

Thanks for the message. The major issue appears to be problems in generating the Vcc-relative information, but some general supply issues are cropping up too. Assuming this is just a regular I/O buffer without internal terminations...

1) I would expect the Pullup I-V tables to pass through the zero V, zero I axis intercept. Yet they do not, with the max and min data shifted by ~0.3 V above and below 0 V, respectively. This suggests that the math used to generate the tables may be incorrect. Remember that, if the data at Vout is collected ground-relative, you can make the power clamp and pullup table data in Vcc-relative by the formula (Vtable_corner = Vcc_corner - Vout_corner), where xxx_corner refers to a value collected for typ, min or max. For example, if Vcc_min is 4.5 V, data collected ground-relative for 0.0 at the output would be entered in the table for the 4.5 V row.

The supply voltages and the Pullup I-V axis intercepts (when plotted ground-relative) don't agree, which implies a problem with the supply listed for the [Voltage Range] keyword not matching either the real circuit or the values used to generate the Vcc-relative tables.

2) The voltage for the buffer is 5 V +/- 0.5, but the V-t fixture is 3.3 V +/- 0.3 V. This complicates the math (it gets very hard for me to calculate the intercepts if they don't match, at least before my first cup of coffee), but it also suggests that the buffer V-t and I-V data sets were collected using different settings or otherwise using different conditions. I would recommend checking the actual fixtures used for the V-t extraction; matching the fixture voltages to the voltage supply would make checking easier.

Calculating the right I-V intercepts vs. V-t levels will be easier once these issues are addressed.

- Michael Mirmak

Intel Corp.

Chair, EIA IBIS Open Forum

From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On Behalf Of Sudarshan H N
Sent: Thursday, October 18, 2007 2:16 AM
To: ibis@server.eda.org; ibis-users@server.eda.org
Subject: [IBIS] I-V and V-t curve mismatch

Hello Experts,

I am finding problem with one of my IBIS model in I-V and V-t curve mismatch. Please find the attached model for the refernence.

ERROR - Model dummy: The [Rising Waveform]
      with [R_fixture]=80 Ohms and [V_fixture]=0V
      has TYP column DC endpoints of 0.01V and 2.66v, but
      an equivalent load applied to the model's I-V tables yields
      different voltages (-0.00V and 3.90V),
      a difference of 0.25% and 31.85%, respectively.

I wrote a new tool to generate IBIS models and i am not able to make out where it is going wrong.
I actually tried to manually calculate the currents at the points , that it has reported in the above error.

As it is a rising waveform having a R_fixture to ground the current at 2.66v (steady state) would be 2.66v/50 = 33.25mA.

I looked at the voltage corresponding to 33.25mA in pullup table and i found it is coming around 0.66v. There is a mismatch in the way i am caluculating also. But i observed a different voltage of 0.66v compared to what ibischk4 has reported i.e, 3.9v.

Let me know is the way i am cross checking is correct or not ? If not let me know the exact procedure.

Also let me know what might have been gone wrong in the curves. From the shape of the curves i am not seeing any problem with the way i have generated.

Please let me know your answers as soon as possible.

Note : Please dont consider any other values apart from the curves like Ramp , C_comp etc as i have dummy values for these place holders.

Thanks & Regards
Sudarshan

--
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. - ------=_Part_4972_15517274.1192771928040-- - -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail majordomo@eda-stds.org |with the appropriate command message(s) in the body: | | help | subscribe ibis | subscribe ibis-users | unsubscribe ibis | unsubscribe ibis-users | |or e-mail a request to ibis-request@eda-stds.org. | |IBIS reflector archives exist under: | | http://www.eda-stds.org/pub/ibis/email_archive/ Recent | http://www.eda-stds.org/pub/ibis/users_archive/ Recent | http://www.eda-stds.org/pub/ibis/email/ E-mail since 1993 ------------------------------ Date: Mon, 22 Oct 2007 20:12:38 +0530 From: "Sudarshan H N" Subject: [IBIS-Users] Re: [IBIS] I-V and V-t curve mismatch - ------=_Part_16825_4484738.1193064158225 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline Hi Michael & All, Can you people answer to my question regarding the voltage ranges in MIN and MAX case as explained below. As Arpad mentioned in one of the earlier mails the range for MIN and MAX case is typ: -3.3 to 6.6 min: -3.6 to 6.3 max: -3.0 to 6.9 How do we select this range for MIN and MAX case. Is there any document which explains the selection criteria for these corners ? If there is no logic , then how can we decide if the supply is 1.8 V supply or 2.5V supply? Let me know your answers. Regards Sudarshan On 10/19/07, Sudarshan H N < hn.sudarshan@gmail.com> wrote: > > Hi Michael, > > Thanks for your detailed reponse. I made a small mistake in putting the > voltage ranges as you mentioned. As i was writing a new tool , at this point > of time i didnt give much attention to printing correct voltage range , and > i was only worried about the correct extraction of V-t and I-V tables. > > I have considered the formula you have mentioned for calculating > Vcc-relative Pullup and Powerclamp tables. I changed the voltage range to ( > 3.3, 3.0 and 3.6 which is the actual case) and now i am able to get rid of > all these errors. > > But still i have one query regarding the values for I-V curves when it is > in the Min or MAX corner. I asked about this in my previous mail. Lynne and > Arpad gave some answers but that didnt solve my problem. > > The problem with MIN and MAX corner is , what is the voltage range we need > to consider for MIN and MAX case . For example if we consider 3.3 V > supply, the typical range would be -3.3 to 6.6 and this is the voltage > range in the IBIS file for all 3 corners. As per the cookbook we need to > consider voltage range -Vcc to +2Vcc and hence for the MIN case the range > will be -3.0 to +6.0. So in that case what current values we need to put > for the voltage range -3.3 to -3.0 and +6.0 to +6.6 whose values will be > missing in MIN corner simulations. > > I hope i have explained the problem correctly and let me know your > answers. > > Thanks & Regards > Sudarshan > > > On 10/18/07, Mirmak, Michael wrote: > > > > Sudarshan, > > > > Thanks for the message. The major issue appears to be problems in > > generating the Vcc-relative information, but some general supply issues are > > cropping up too. Assuming this is just a regular I/O buffer without > > internal terminations... > > > > 1) I would expect the Pullup I-V tables to pass through the zero V, zero > > I axis intercept. Yet they do not, with the max and min data shifted by > > ~0.3 V above and below 0 V, respectively. This suggests that the math used > > to generate the tables may be incorrect. Remember that, if the data at Vout > > is collected ground-relative, you can make the power clamp and pullup table > > data in Vcc-relative by the formula (Vtable_corner = Vcc_corner - > > Vout_corner), where xxx_corner refers to a value collected for typ, min or > > max. For example, if Vcc_min is 4.5 V, data collected ground-relative > > for 0.0 at the output would be entered in the table for the 4.5 V row. > > > > The supply voltages and the Pullup I-V axis intercepts (when plotted > > ground-relative) don't agree, which implies a problem with the supply > > listed for the [Voltage Range] keyword not matching either the real circuit > > or the values used to generate the Vcc-relative tables. > > > > 2) The voltage for the buffer is 5 V +/- 0.5, but the V-t fixture is 3.3V +/- > > 0.3 V. This complicates the math (it gets very hard for me to calculate > > the intercepts if they don't match, at least before my first cup of coffee), > > but it also suggests that the buffer V-t and I-V data sets were collected > > using different settings or otherwise using different conditions. I would > > recommend checking the actual fixtures used for the V-t extraction; matching > > the fixture voltages to the voltage supply would make checking easier. > > > > Calculating the right I-V intercepts vs. V-t levels will be easier once > > these issues are addressed. > > > > - Michael Mirmak > > Intel Corp. > > Chair, EIA IBIS Open Forum > > > > ------------------------------ > > *From:* owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] *On > > Behalf Of *Sudarshan H N > > *Sent:* Thursday, October 18, 2007 2:16 AM > > *To:* ibis@server.eda.org; ibis-users@server.eda.org > > *Subject:* [IBIS] I-V and V-t curve mismatch > > > > Hello Experts, > > > > I am finding problem with one of my IBIS model in I-V and V-t curve > > mismatch. Please find the attached model for the refernence. > > > > ERROR - Model dummy: The [Rising Waveform] > > with [R_fixture]=80 Ohms and [V_fixture]=0V > > has TYP column DC endpoints of 0.01V and 2.66v, but > > an equivalent load applied to the model's I-V tables yields > > different voltages (-0.00V and 3.90V), > > a difference of 0.25% and 31.85%, respectively. > > > > I wrote a new tool to generate IBIS models and i am not able to make out > > where it is going wrong. > > I actually tried to manually calculate the currents at the points , that > > it has reported in the above error. > > > > As it is a rising waveform having a R_fixture to ground the current at > > 2.66v (steady state) would be 2.66v/50 = 33.25mA. > > > > I looked at the voltage corresponding to 33.25mA in pullup table and i > > found it is coming around 0.66v. There is a mismatch in the way i am > > caluculating also. But i observed a different voltage of 0.66v compared > > to what ibischk4 has reported i.e, 3.9v. > > > > Let me know is the way i am cross checking is correct or not ? If not > > let me know the exact procedure. > > > > Also let me know what might have been gone wrong in the curves. From the > > shape of the curves i am not seeing any problem with the way i have > > generated. > > > > Please let me know your answers as soon as possible. > > > > Note : Please dont consider any other values apart from the curves like > > Ramp , C_comp etc as i have dummy values for these place holders. > > > > Thanks & Regards > > Sudarshan > > > > > > > > -- > > 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. - ------=_Part_16825_4484738.1193064158225 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline Hi Michael & All,

Can you people answer to my question regarding the voltage ranges in MIN and MAX case as explained below. As Arpad mentioned in one of the earlier mails the range for MIN and MAX case is

typ: -3.3 to 6.6

min: -3.6 to 6.3

max: -3.0 to 6.9

How do we select this range for MIN and MAX case. Is there any document which explains the selection criteria for these corners ? If there is no logic , then how can we decide if the supply is 1.8 V supply or 2.5V supply?

Let me know your answers.

Regards
Sudarshan

On 10/19/07, Sudarshan H N < hn.sudarshan@gmail.com> wrote:

Hi Michael,

Thanks for your detailed reponse. I made a small mistake in putting the voltage ranges as you mentioned. As i was writing a new tool , at this point of time i didnt give much attention to printing correct voltage range , and i was only worried about the correct extraction of V-t and I-V tables.

I have considered the formula you have mentioned for calculating Vcc-relative Pullup and Powerclamp tables. I changed the voltage range to (3.3, 3.0 and 3.6 which is the actual case) and now i am able to get rid of all these errors.

But still i have one query regarding the values for I-V curves when it is in the Min or MAX corner. I asked about this in my previous mail. Lynne and Arpad gave some answers but that didnt solve my problem.

The problem with MIN and MAX corner is , what is the voltage range we need to consider for MIN and MAX case . For example if we consider 3.3 V supply, the typical range would be -3.3 to 6.6 and this is the voltage range in the IBIS file for all 3 corners. As per the cookbook we need to consider voltage range -Vcc to +2Vcc and hence for the MIN case the range will be -3.0 to +6.0. So in that case what current values we need to put for the voltage range -3.3 to -3.0 and +6.0 to +6.6 whose values will be missing in MIN corner simulations.

I hope i have explained the problem correctly and let me know your answers.

Thanks & Regards
Sudarshan

On 10/18/07, Mirmak, Michael <michael.mirmak@intel.com > wrote:

Sudarshan,

Thanks for the message. The major issue appears to be problems in generating the Vcc-relative information, but some general supply issues are cropping up too. Assuming this is just a regular I/O buffer without internal terminations...

1) I would expect the Pullup I-V tables to pass through the zero V, zero I axis intercept. Yet they do not, with the max and min data shifted by ~0.3 V above and below 0 V, respectively. This suggests that the math used to generate the tables may be incorrect. Remember that, if the data at Vout is collected ground-relative, you can make the power clamp and pullup table data in Vcc-relative by the formula (Vtable_corner = Vcc_corner - Vout_corner), where xxx_corner refers to a value collected for typ, min or max. For example, if Vcc_min is 4.5 V, data collected ground-relative for 0.0 at the output would be entered in the table for the 4.5 V row.

The supply voltages and the Pullup I-V axis intercepts (when plotted ground-relative) don't agree, which implies a problem with the supply listed for the [Voltage Range] keyword not matching either the real circuit or the values used to generate the Vcc-relative tables.

2) The voltage for the buffer is 5 V +/- 0.5, but the V-t fixture is 3.3 V +/- 0.3 V. This complicates the math (it gets very hard for me to calculate the intercepts if they don't match, at least before my first cup of coffee), but it also suggests that the buffer V-t and I-V data sets were collected using different settings or otherwise using different conditions. I would recommend checking the actual fixtures used for the V-t extraction; matching the fixture voltages to the voltage supply would make checking easier.

Calculating the right I-V intercepts vs. V-t levels will be easier once these issues are addressed.

- Michael Mirmak

Intel Corp.

Chair, EIA IBIS Open Forum

From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On Behalf Of Sudarshan H N
Sent: Thursday, October 18, 2007 2:16 AM
To: ibis@server.eda.org; ibis-users@server.eda.org
Subject: [IBIS] I-V and V-t curve mismatch

Hello Experts,

I am finding problem with one of my IBIS model in I-V and V-t curve mismatch. Please find the attached model for the refernence.

ERROR - Model dummy: The [Rising Waveform]
      with [R_fixture]=80 Ohms and [V_fixture]=0V
      has TYP column DC endpoints of 0.01V and 2.66v, but
      an equivalent load applied to the model's I-V tables yields
      different voltages (-0.00V and 3.90V),
      a difference of 0.25% and 31.85%, respectively.

I wrote a new tool to generate IBIS models and i am not able to make out where it is going wrong.
I actually tried to manually calculate the currents at the points , that it has reported in the above error.

As it is a rising waveform having a R_fixture to ground the current at 2.66v (steady state) would be 2.66v/50 = 33.25mA.

I looked at the voltage corresponding to 33.25mA in pullup table and i found it is coming around 0.66v. There is a mismatch in the way i am caluculating also. But i observed a different voltage of 0.66v compared to what ibischk4 has reported i.e, 3.9v.

Let me know is the way i am cross checking is correct or not ? If not let me know the exact procedure.

Also let me know what might have been gone wrong in the curves. From the shape of the curves i am not seeing any problem with the way i have generated.

Please let me know your answers as soon as possible.

Note : Please dont consider any other values apart from the curves like Ramp , C_comp etc as i have dummy values for these place holders.

Thanks & Regards
Sudarshan

--
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. - ------=_Part_16825_4484738.1193064158225-- - -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail majordomo@eda-stds.org |with the appropriate command message(s) in the body: | | help | subscribe ibis | subscribe ibis-users | unsubscribe ibis | unsubscribe ibis-users | |or e-mail a request to ibis-request@eda-stds.org. | |IBIS reflector archives exist under: | | http://www.eda-stds.org/pub/ibis/email_archive/ Recent | http://www.eda-stds.org/pub/ibis/users_archive/ Recent | http://www.eda-stds.org/pub/ibis/email/ E-mail since 1993 ------------------------------ Date: Mon, 22 Oct 2007 09:10:53 -0700 From: "Tom Dagostino" Subject: [IBIS-Users] RE: [IBIS] I-V and V-t curve mismatch This is a multipart message in MIME format. - ------=_NextPart_000_0001_01C8148B.742D13A0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Model all three corners from -Vdd to 2*Vdd where Vdd is the typical voltage. Tom Dagostino Teraspeed(R) Labs 13610 SW Harness Lane Beaverton, OR 97008 503-430-1065 tom@teraspeed.com www.teraspeed.com Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 401-284-1827 From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On Behalf Of Sudarshan H N Sent: Monday, October 22, 2007 7:43 AM To: Mirmak, Michael Cc: ibis@server.eda.org; ibis-users@server.eda.org Subject: Re: [IBIS] I-V and V-t curve mismatch Hi Michael & All, Can you people answer to my question regarding the voltage ranges in MIN and MAX case as explained below. As Arpad mentioned in one of the earlier mails the range for MIN and MAX case is typ: -3.3 to 6.6 min: -3.6 to 6.3 max: -3.0 to 6.9 How do we select this range for MIN and MAX case. Is there any document which explains the selection criteria for these corners ? If there is no logic , then how can we decide if the supply is 1.8 V supply or 2.5V supply? Let me know your answers. Regards Sudarshan On 10/19/07, Sudarshan H N < hn.sudarshan@gmail.com> wrote: Hi Michael, Thanks for your detailed reponse. I made a small mistake in putting the voltage ranges as you mentioned. As i was writing a new tool , at this point of time i didnt give much attention to printing correct voltage range , and i was only worried about the correct extraction of V-t and I-V tables. I have considered the formula you have mentioned for calculating Vcc-relative Pullup and Powerclamp tables. I changed the voltage range to (3.3, 3.0 and 3.6 which is the actual case) and now i am able to get rid of all these errors. But still i have one query regarding the values for I-V curves when it is in the Min or MAX corner. I asked about this in my previous mail. Lynne and Arpad gave some answers but that didnt solve my problem. The problem with MIN and MAX corner is , what is the voltage range we need to consider for MIN and MAX case . For example if we consider 3.3 V supply, the typical range would be -3.3 to 6.6 and this is the voltage range in the IBIS file for all 3 corners. As per the cookbook we need to consider voltage range -Vcc to +2Vcc and hence for the MIN case the range will be -3.0 to +6.0. So in that case what current values we need to put for the voltage range -3.3 to -3.0 and +6.0 to +6.6 whose values will be missing in MIN corner simulations. I hope i have explained the problem correctly and let me know your answers. Thanks & Regards Sudarshan On 10/18/07, Mirmak, Michael wrote: Sudarshan, Thanks for the message. The major issue appears to be problems in generating the Vcc-relative information, but some general supply issues are cropping up too. Assuming this is just a regular I/O buffer without internal terminations... 1) I would expect the Pullup I-V tables to pass through the zero V, zero I axis intercept. Yet they do not, with the max and min data shifted by ~0.3 V above and below 0 V, respectively. This suggests that the math used to generate the tables may be incorrect. Remember that, if the data at Vout is collected ground-relative, you can make the power clamp and pullup table data in Vcc-relative by the formula (Vtable_corner = Vcc_corner - Vout_corner), where xxx_corner refers to a value collected for typ, min or max. For example, if Vcc_min is 4.5 V, data collected ground-relative for 0.0 at the output would be entered in the table for the 4.5 V row. The supply voltages and the Pullup I-V axis intercepts (when plotted ground-relative) don't agree, which implies a problem with the supply listed for the [Voltage Range] keyword not matching either the real circuit or the values used to generate the Vcc-relative tables. 2) The voltage for the buffer is 5 V +/- 0.5, but the V-t fixture is 3.3 V +/- 0.3 V. This complicates the math (it gets very hard for me to calculate the intercepts if they don't match, at least before my first cup of coffee), but it also suggests that the buffer V-t and I-V data sets were collected using different settings or otherwise using different conditions. I would recommend checking the actual fixtures used for the V-t extraction; matching the fixture voltages to the voltage supply would make checking easier. Calculating the right I-V intercepts vs. V-t levels will be easier once these issues are addressed. - - Michael Mirmak Intel Corp. Chair, EIA IBIS Open Forum _____ From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On Behalf Of Sudarshan H N Sent: Thursday, October 18, 2007 2:16 AM To: ibis@server.eda.org; ibis-users@server.eda.org Subject: [IBIS] I-V and V-t curve mismatch Hello Experts, I am finding problem with one of my IBIS model in I-V and V-t curve mismatch. Please find the attached model for the refernence. ERROR - Model dummy: The [Rising Waveform] with [R_fixture]=80 Ohms and [V_fixture]=0V has TYP column DC endpoints of 0.01V and 2.66v, but an equivalent load applied to the model's I-V tables yields different voltages (-0.00V and 3.90V), a difference of 0.25% and 31.85%, respectively. I wrote a new tool to generate IBIS models and i am not able to make out where it is going wrong. I actually tried to manually calculate the currents at the points , that it has reported in the above error. As it is a rising waveform having a R_fixture to ground the current at 2.66v (steady state) would be 2.66v/50 = 33.25mA. I looked at the voltage corresponding to 33.25mA in pullup table and i found it is coming around 0.66v. There is a mismatch in the way i am caluculating also. But i observed a different voltage of 0.66v compared to what ibischk4 has reported i.e, 3.9v. Let me know is the way i am cross checking is correct or not ? If not let me know the exact procedure. Also let me know what might have been gone wrong in the curves. From the shape of the curves i am not seeing any problem with the way i have generated. Please let me know your answers as soon as possible. Note : Please dont consider any other values apart from the curves like Ramp , C_comp etc as i have dummy values for these place holders. Thanks & Regards Sudarshan - -- 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. - -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. - ------=_NextPart_000_0001_01C8148B.742D13A0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Model all three corners from –Vdd to 2*Vdd where Vdd is the typical voltage.

Tom Dag= ostino
Teraspeed(R) Labs
13610 SW Harness Lane
Beaverton, OR 97008
503-430-1065
tom@teraspeed.com
www.teraspeed.com

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

From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On Behalf O= f Sudarshan H N
Sent: Monday, October 22, 2007 7:43 AM
To: Mirmak, Michael
Cc: ibis@server.eda.org; ibis-users@server.eda.org
Subject: Re: [IBIS] I-V and V-t curve mismatch

Hi Michael & All,
Can you people answer to my question regarding the voltage ranges in MIN and MAX case as explained below. As Arpad mentioned in one of the earlier mails= the range for MIN and MAX case is

typ: - -3.3 to 6.6

min: - -3.6 to 6.3

max: -3.0 to 6.9

How do we select this range for MIN and MAX case. Is there any docum= ent which explains the selection criteria for these corners ? If there is no lo= gic , then how can we decide if the supply is 1.8 V supply or 2.5V supply?

Let me know your answers.

Regards
Sudarshan

On 10/19/07, Sudarshan H N= < hn.sudarsh= an@gmail.com> wrote:

Hi Michael,

Thanks for your detailed reponse. I made a small mistake in putting the vol= tage ranges as you mentioned. As i was writing a new tool , at this point of tim= e i didnt give much attention to printing correct voltage range , and i w= as only worried about the correct extraction of V-t and I-V tables.

I have considered the formula you have mentioned for calculating Vcc-relati= ve Pullup and Powerclamp tables. I changed the voltage range to (3.3, 3.0 and = 3.6 which is the actual case) and now i am able to get rid of all these errors.=

But still i have one query regarding the values for I-V curves when it is in the Min or MAX corner. I asked about this in my previous mail. Lynne and Ar= pad gave some answers but that didnt solve my problem.

The problem with MIN and MAX corner is , what is the voltage range we need = to consider for MIN and MAX case . For example if we consider 3.3 V supply, the typical range would be -3.3 to 6.6 and this is the voltage range in the IBIS file for all 3 corners. As per the cookbook we need to consider voltage ran= ge - -Vcc to +2Vcc and hence for the MIN case the range will be -3.0 to +6.0. So= in that case what current values we need to put for the voltage range -3.3 to = - -3.0 and +6.0 to +6.6 whose values will be missing in MIN corner simulations.

I hope i have explained the problem correctly and let me know your answers.=

Thanks & Regards
Sudarshan

On 10/18/07, Mirmak, Micha= el <michael.m= irmak@intel.com > wrote:

Sudarshan,

Thanks for the message. The major issue appears to be problems in generating the Vcc-relative information, but some general supply issues are cropping up too. Assuming this is just a regular I/O buffer without internal terminations...

1) I would expect the Pullup I-V tables to pass through the zer= o V, zero I axis intercept. Yet they do not, with the max and min data shi= fted by ~0.3 V above and below 0 V, respectively. This suggests that the m= ath used to generate the tables may be incorrect. Remember that, if = the data at Vout is collected ground-relative, you can make the power clamp and pullup table data in Vcc-relative by the formula (Vtable_corner =3D Vcc_cor= ner - Vout_corner), where xxx_corner refers to a value collected for typ, min or max. For example, if Vcc_min is 4.5 V, data collected ground-relative for 0.0 at the output would be entered in the table for the 4.5 V row.

The supply voltages and the Pullup I-V axis intercepts (when plotted ground-relative) don't agree, which implies a problem with the supp= ly listed for the [Voltage Range] keyword not matching either the real circuit or the values used to generate the Vcc-relative tables.=

2) The voltage for the buffer is 5 V +/- 0.5, but the V-t fixtu= re is 3.3 V +/- 0.3 V. This complicates the math (it gets very hard for = me to calculate the intercepts if they don't match, at least before my first c= up of coffee), but it also suggests that the buffer V-t and I-V data sets were collected using different settings or otherwise using different conditions. I would recommend checking the actual fixtures used for t= he V-t extraction; matching the fixture voltages to the voltage supply would m= ake checking easier.

Calculating the right I-V intercepts vs. V-t levels will be eas= ier once these issues are addressed.

- Michael Mirmak

Intel Corp.

Chair, EIA IBIS Open Forum

From: owner-ibis@server.eda.org [mailto:owner-ibis@serv= er.eda.org] On Behalf Of Sudarshan H N
Sent: Thursday, October 18, 2007 2:16 AM
To: ibis@se= rver.eda.org; ibis-users@s= erver.eda.org
Subject: [IBIS] I-V and V-t curve mismatch

Hello Experts,

I am finding problem with one of my IBIS model in I-V and V-t curve mismatc= h. Please find the attached model for the refernence.

ERROR - Model dummy: The [Rising Waveform]
      with [R_fixture]=3D80 Ohms and [V_fixture]= =3D0V
      has TYP column DC endpoints of 0.01V and 2.66v, but
      an equivalent load applied to the model's I-V tables yields
      different voltages (-0.00V and 3.90V),=
      a difference of 0.25% and 31.85%, respectively.

I wrote a new tool to generate IBIS models and i am not able to make out wh= ere it is going wrong.
I actually tried to manually calculate the currents at the points , that it= has reported in the above error.

As it is a rising waveform having a R_fixture to ground the current at 2.66v (steady state) would be 2.66v/50 =3D 33.25mA.

I looked at the voltage corresponding to 33.25mA in pullup table and i foun= d it is coming around 0.66v. There is a mismatch in the way i am caluculating al= so. But i observed a different voltage of 0.66v compared to what ibischk4 has r= eported i.e, 3.9v.

Let me know is the way i am cross checking is correct or not ? If not let me know the exact procedure.

Also let me know what might have been gone wrong in the curves. From the sh= ape of the curves i am not seeing any problem with the way i have generated.
Please let me know your answers as soon as possible.

Note : Please dont consider any other values apart from the curves like Ram= p , C_comp etc as i have dummy values for these place holders.

Thanks & Regards
Sudarshan

--
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. - ------=_NextPart_000_0001_01C8148B.742D13A0-- - -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail majordomo@eda-stds.org |with the appropriate command message(s) in the body: | | help | subscribe ibis | subscribe ibis-users | unsubscribe ibis | unsubscribe ibis-users | |or e-mail a request to ibis-request@eda-stds.org. | |IBIS reflector archives exist under: | | http://www.eda-stds.org/pub/ibis/email_archive/ Recent | http://www.eda-stds.org/pub/ibis/users_archive/ Recent | http://www.eda-stds.org/pub/ibis/email/ E-mail since 1993 ------------------------------ Date: Mon, 22 Oct 2007 13:09:24 -0400 From: "Todd Westerhoff" Subject: [IBIS-Users] RE: [IBIS] I-V and V-t curve mismatch This is a multi-part message in MIME format. - ------=_NextPart_000_0070_01C814AC.C49AAA20 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit I agree with Tom. The choice of -2*VDD to 2*VDD is somewhat arbitrary . it's simply meant to ensure that you have valid V/I data for any voltage that the part will be exposed to. Thus, you don't need to adjust the voltage ranges based on the MIN and MAX cases. For most technologies, if you have overshoot that's equal to the supply voltage, you have bigger problems than model accuracy ! 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 _____ From: owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf Of Tom Dagostino Sent: Monday, October 22, 2007 12:11 PM To: 'Sudarshan H N'; 'Mirmak, Michael' Cc: ibis@eda.org; ibis-users@eda.org Subject: RE: [IBIS] I-V and V-t curve mismatch Model all three corners from -Vdd to 2*Vdd where Vdd is the typical voltage. Tom Dagostino Teraspeed(R) Labs 13610 SW Harness Lane Beaverton, OR 97008 503-430-1065 tom@teraspeed.com www.teraspeed.com Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 401-284-1827 From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On Behalf Of Sudarshan H N Sent: Monday, October 22, 2007 7:43 AM To: Mirmak, Michael Cc: ibis@server.eda.org; ibis-users@server.eda.org Subject: Re: [IBIS] I-V and V-t curve mismatch Hi Michael & All, Can you people answer to my question regarding the voltage ranges in MIN and MAX case as explained below. As Arpad mentioned in one of the earlier mails the range for MIN and MAX case is typ: -3.3 to 6.6 min: -3.6 to 6.3 max: -3.0 to 6.9 How do we select this range for MIN and MAX case. Is there any document which explains the selection criteria for these corners ? If there is no logic , then how can we decide if the supply is 1.8 V supply or 2.5V supply? Let me know your answers. Regards Sudarshan On 10/19/07, Sudarshan H N < hn.sudarshan@gmail.com> wrote: Hi Michael, Thanks for your detailed reponse. I made a small mistake in putting the voltage ranges as you mentioned. As i was writing a new tool , at this point of time i didnt give much attention to printing correct voltage range , and i was only worried about the correct extraction of V-t and I-V tables. I have considered the formula you have mentioned for calculating Vcc-relative Pullup and Powerclamp tables. I changed the voltage range to (3.3, 3.0 and 3.6 which is the actual case) and now i am able to get rid of all these errors. But still i have one query regarding the values for I-V curves when it is in the Min or MAX corner. I asked about this in my previous mail. Lynne and Arpad gave some answers but that didnt solve my problem. The problem with MIN and MAX corner is , what is the voltage range we need to consider for MIN and MAX case . For example if we consider 3.3 V supply, the typical range would be -3.3 to 6.6 and this is the voltage range in the IBIS file for all 3 corners. As per the cookbook we need to consider voltage range -Vcc to +2Vcc and hence for the MIN case the range will be -3.0 to +6.0. So in that case what current values we need to put for the voltage range -3.3 to -3.0 and +6.0 to +6.6 whose values will be missing in MIN corner simulations. I hope i have explained the problem correctly and let me know your answers. Thanks & Regards Sudarshan On 10/18/07, Mirmak, Michael wrote: Sudarshan, Thanks for the message. The major issue appears to be problems in generating the Vcc-relative information, but some general supply issues are cropping up too. Assuming this is just a regular I/O buffer without internal terminations... 1) I would expect the Pullup I-V tables to pass through the zero V, zero I axis intercept. Yet they do not, with the max and min data shifted by ~0.3 V above and below 0 V, respectively. This suggests that the math used to generate the tables may be incorrect. Remember that, if the data at Vout is collected ground-relative, you can make the power clamp and pullup table data in Vcc-relative by the formula (Vtable_corner = Vcc_corner - Vout_corner), where xxx_corner refers to a value collected for typ, min or max. For example, if Vcc_min is 4.5 V, data collected ground-relative for 0.0 at the output would be entered in the table for the 4.5 V row. The supply voltages and the Pullup I-V axis intercepts (when plotted ground-relative) don't agree, which implies a problem with the supply listed for the [Voltage Range] keyword not matching either the real circuit or the values used to generate the Vcc-relative tables. 2) The voltage for the buffer is 5 V +/- 0.5, but the V-t fixture is 3.3 V +/- 0.3 V. This complicates the math (it gets very hard for me to calculate the intercepts if they don't match, at least before my first cup of coffee), but it also suggests that the buffer V-t and I-V data sets were collected using different settings or otherwise using different conditions. I would recommend checking the actual fixtures used for the V-t extraction; matching the fixture voltages to the voltage supply would make checking easier. Calculating the right I-V intercepts vs. V-t levels will be easier once these issues are addressed. - - Michael Mirmak Intel Corp. Chair, EIA IBIS Open Forum _____ From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On Behalf Of Sudarshan H N Sent: Thursday, October 18, 2007 2:16 AM To: ibis@server.eda.org; ibis-users@server.eda.org Subject: [IBIS] I-V and V-t curve mismatch Hello Experts, I am finding problem with one of my IBIS model in I-V and V-t curve mismatch. Please find the attached model for the refernence. ERROR - Model dummy: The [Rising Waveform] with [R_fixture]=80 Ohms and [V_fixture]=0V has TYP column DC endpoints of 0.01V and 2.66v, but an equivalent load applied to the model's I-V tables yields different voltages (-0.00V and 3.90V), a difference of 0.25% and 31.85%, respectively. I wrote a new tool to generate IBIS models and i am not able to make out where it is going wrong. I actually tried to manually calculate the currents at the points , that it has reported in the above error. As it is a rising waveform having a R_fixture to ground the current at 2.66v (steady state) would be 2.66v/50 = 33.25mA. I looked at the voltage corresponding to 33.25mA in pullup table and i found it is coming around 0.66v. There is a mismatch in the way i am caluculating also. But i observed a different voltage of 0.66v compared to what ibischk4 has reported i.e, 3.9v. Let me know is the way i am cross checking is correct or not ? If not let me know the exact procedure. Also let me know what might have been gone wrong in the curves. From the shape of the curves i am not seeing any problem with the way i have generated. Please let me know your answers as soon as possible. Note : Please dont consider any other values apart from the curves like Ramp , C_comp etc as i have dummy values for these place holders. Thanks & Regards Sudarshan - -- 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. - -- 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. - ------=_NextPart_000_0070_01C814AC.C49AAA20 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

I agree with Tom.

The choice of -2*VDD to 2*VDD is somew= hat arbitrary … it’s simply meant to ensure that you have valid V/I data for any voltage that the part will be exposed to. Thus, you don&= #8217;t need to adjust the voltage ranges based on the MIN and MAX cases. For most technologies, if you have overshoot that’s equal to the supply voltage, you have bigger problems than model accuracy !

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

From: owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf Of Tom Dagostino
Sent: Monday, October 22, 20= 07 12:11 PM
To: 'Sudarshan H N'; 'Mirmak, Michael'
Cc: ibis@eda.org; ibis-users@eda.org
Subject: RE: [IBIS] I-V and = V-t curve mismatch

Model all three corners from –Vdd to 2*Vdd where Vdd is the typical voltage.

Tom Dagostino
Teraspeed(R) Labs
13610 SW Harness Lane
Beaverton, OR 97008
503-430-1065
tom@teraspeed.com
www.teraspeed.com

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

From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On Behalf Of Sudarshan H N
Sent: Monday, October 22, 20= 07 7:43 AM
To: Mirmak, Michael
Cc: ibis@server.eda.org; ibis-users@server.eda.org
Subject: Re: [IBIS] I-V and = V-t curve mismatch

Hi Michael & = All,

Can you people answer to my question regarding the voltage ranges in MIN and MAX case as explained below. As Arpad mentioned in one of the earlier mails= the range for MIN and MAX case is

typ: -3.3 to 6.6<= /p>
min: -3.6 to 6.3<= /p>
max: -3.0 to 6.9=

How do we select this range for MIN and MAX case. Is there any document which explains the selection criteria for these corners ? If there= is no logic , then how can we decide if the supply is 1.8 V supply or 2.5V sup= ply?

Let me know your answers.

Regards
Sudarshan

=

On 10/19/07, Sudarshan H N < hn.sudarshan@gmail.com> wrote:

Hi Michael,

Thanks for your detailed reponse. I made a small mistake in putting the vol= tage ranges as you mentioned. As i was writing a new tool , at this point of tim= e i didnt give much attention to printing correct voltage range , and i w= as only worried about the correct extraction of V-t and I-V tables.

I have considered the formula you have mentioned for calculating Vcc-relati= ve Pullup and Powerclamp tables. I changed the voltage range to (3.3, 3.0 and = 3.6 which is the actual case) and now i am able to get rid of all these errors.=

But still i have one query regarding the values for I-V curves when it is in the Min or MAX corner. I asked about this in my previous mail. Lynne and Ar= pad gave some answers but that didnt solve my problem.

The problem with MIN and MAX corner is , what is the voltage range we need = to consider for MIN and MAX case . For example if we consider 3.3 V supply, the typical range would be -3.3 to 6.6 and this is the voltage range in the IBIS file for all 3 corners. As per the cookbook we need to consider voltage ran= ge - -Vcc to +2Vcc and hence for the MIN case the range will be -3.0 to +6.0. So= in that case what current values we need to put for the voltage range -3.3 to = - -3.0 and +6.0 to +6.6 whose values will be missing in MIN corner simulations.

I hope i have explained the problem correctly and let me know your answers.=

Thanks & Regards
Sudarshan

On 10/18/07, Mirmak, Michael <michael.mirmak@intel.com > wrote:

Sudarshan,

Thanks for the message. The major issue appears to be problems in generating the Vcc-relative information, but some general supply issues are cropping up too. Assuming this is just= a regular I/O buffer without internal terminations...

1) I would expect the Pullup I-V table= s to pass through the zero V, zero I axis intercept. Yet they do not, with= the max and min data shifted by ~0.3 V above and below 0 V, respectively. This suggests that the math used to generate the tables may be incorrect.&n= bsp; Remember that, if the data at Vout is collected ground-relative, you c= an make the power clamp and pullup table data in Vcc-relative by the formula (Vtable_corner =3D Vcc_corner - Vout_corner), where xxx_corner refers to a = value collected for typ, min or max. For example, if Vcc_min is 4.5 V, data collected ground-relative for 0.0 at the output would be enter= ed in the table for the 4.5 V row.

The supply voltages and the Pullup I-V axis intercepts (when plotted ground-relative) don't agree, which implies a problem with the supply listed for the [Voltage Range] keyword not matching either the real circuit or the values used to generate the Vcc-relative tables.

2) The voltage for the buffer is 5 V += /- 0.5, but the V-t fixture is 3.3 V +/- 0.3 V. This complicates the math (it gets very hard for me to calculate the intercepts if they don't match, = at least before my first cup of coffee), but it also suggests that the buffer = V-t and I-V data sets were collected using different settings or otherwise using different conditions. I would recommend checking the actual fixtures = used for the V-t extraction; matching the fixture voltages to the voltage supply would make checking easier.

Calculating the right I-V intercepts v= s. V-t levels will be easier once these issues are addressed.

- Michael Mirmak

Intel Corp.<= /o:p>

Chair, EIA IBIS Open Forum

From:= = owner-ibis@serv= er.eda.org [mailto:owne= r-ibis@server.eda.org] On Behalf Of Sudarshan H N Sent: Thursday, October 18, = 2007 2:16 AM
To: ibis@server.eda.org; ibis-users@serv= er.eda.org
Subject: [IBIS] I-V and V-t = curve mismatch

Hello Experts,

I am finding problem with one of my IBIS model in I-V and V-t curve mismatc= h. Please find the attached model for the refernence.

ERROR - Model dummy: The [Rising Waveform]
      with [R_fixture]=3D80 Ohms and [V_fixture]= =3D0V
      has TYP column DC endpoints of 0.01V and 2.66v, but
      an equivalent load applied to the model's I-V tables yields
      different voltages (-0.00V and 3.90V),=
      a difference of 0.25% and 31.85%, respectively.

I wrote a new tool to generate IBIS models and i am not able to make out wh= ere it is going wrong.
I actually tried to manually calculate the currents at the points , that it= has reported in the above error.

As it is a rising waveform having a R_fixture to ground the current a= t 2.66v (steady state) would be 2.66v/50 =3D 33.25mA.

I looked at the voltage corresponding to 33.25mA in pullup table and i foun= d it is coming around 0.66v. There is a mismatch in the way i am caluculating al= so. But i observed a different voltage of 0.66v compared to what ibischk4 has reported i.e, 3.9v.

Let me know is the way i am cross checking is correct or not ? If not let me know the exact procedure.

Also let me know what might have been gone wrong in the curves. From the sh= ape of the curves i am not seeing any problem with the way i have generated.
Please let me know your answers as soon as possible.

Note : Please dont consider any other values apart from the curves like Ram= p , C_comp etc as i have dummy values for these place holders.

Thanks & Regards
Sudarshan

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believed to be clean. - ------=_NextPart_000_0070_01C814AC.C49AAA20-- - -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail majordomo@eda-stds.org |with the appropriate command message(s) in the body: | | help | subscribe ibis | subscribe ibis-users | unsubscribe ibis | unsubscribe ibis-users | |or e-mail a request to ibis-request@eda-stds.org. | |IBIS reflector archives exist under: | | http://www.eda-stds.org/pub/ibis/email_archive/ Recent | http://www.eda-stds.org/pub/ibis/users_archive/ Recent | http://www.eda-stds.org/pub/ibis/email/ E-mail since 1993 ------------------------------ Date: Mon, 22 Oct 2007 13:20:03 -0400 From: Scott McMorrow Subject: [IBIS-Users] Re: [IBIS] I-V and V-t curve mismatch This is a multi-part message in MIME format. - --------------000806080808010904070500 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit To follow up with what Tom and Todd have said, modern process technology often will not tolerate voltage swings 1 X Vdd beyond the rails, like older technologies did. In many cases, you will need to adjust your extraction method so that it does not exceed the device breakdown limits, either in Spice or in measurement-based extraction. Scott McMorrow Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 (401) 284-1827 Business (401) 284-1840 Fax http://www.teraspeed.com Teraspeed� is the registered service mark of Teraspeed Consulting Group LLC Todd Westerhoff wrote: > > I agree with Tom. > > > > The choice of -2*VDD to 2*VDD is somewhat arbitrary ... it's simply > meant to ensure that you have valid V/I data for any voltage that the > part will be exposed to. Thus, you don't need to adjust the voltage > ranges based on the MIN and MAX cases. For most technologies, if you > have overshoot that's equal to the supply voltage, you have bigger > problems than model accuracy ! > > > > 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 > > ------------------------------------------------------------------------ > > *From:* owner-ibis@eda.org [mailto:owner-ibis@eda.org] *On Behalf Of > *Tom Dagostino > *Sent:* Monday, October 22, 2007 12:11 PM > *To:* 'Sudarshan H N'; 'Mirmak, Michael' > *Cc:* ibis@eda.org; ibis-users@eda.org > *Subject:* RE: [IBIS] I-V and V-t curve mismatch > > > > Model all three corners from --Vdd to 2*Vdd where Vdd is the typical > voltage. > > > > Tom Dagostino > Teraspeed(R) Labs > 13610 SW Harness Lane > Beaverton, OR 97008 > 503-430-1065 > tom@teraspeed.com > www.teraspeed.com > > Teraspeed Consulting Group LLC > 121 North River Drive > Narragansett, RI 02882 > 401-284-1827 > > *From:* owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] > *On Behalf Of *Sudarshan H N > *Sent:* Monday, October 22, 2007 7:43 AM > *To:* Mirmak, Michael > *Cc:* ibis@server.eda.org; ibis-users@server.eda.org > *Subject:* Re: [IBIS] I-V and V-t curve mismatch > > > > Hi Michael & All, > > Can you people answer to my question regarding the voltage ranges in > MIN and MAX case as explained below. As Arpad mentioned in one of the > earlier mails the range for MIN and MAX case is > > typ: -3.3 to 6.6 > > min: -3.6 to 6.3 > > max: -3.0 to 6.9 > > How do we select this range for MIN and MAX case. Is there any > document which explains the selection criteria for these corners ? If > there is no logic , then how can we decide if the supply is 1.8 V > supply or 2.5V supply? > > Let me know your answers. > > Regards > Sudarshan > > > > On 10/19/07, *Sudarshan H N* < hn.sudarshan@gmail.com > > wrote: > > Hi Michael, > > Thanks for your detailed reponse. I made a small mistake in putting > the voltage ranges as you mentioned. As i was writing a new tool , at > this point of time i didnt give much attention to printing correct > voltage range , and i was only worried about the correct extraction of > V-t and I-V tables. > > I have considered the formula you have mentioned for calculating > Vcc-relative Pullup and Powerclamp tables. I changed the voltage range > to (3.3, 3.0 and 3.6 which is the actual case) and now i am able to > get rid of all these errors. > > But still i have one query regarding the values for I-V curves when it > is in the Min or MAX corner. I asked about this in my previous mail. > Lynne and Arpad gave some answers but that didnt solve my problem. > > The problem with MIN and MAX corner is , what is the voltage range we > need to consider for MIN and MAX case . For example if we consider 3.3 > V supply, the typical range would be -3.3 to 6.6 and this is the > voltage range in the IBIS file for all 3 corners. As per the cookbook > we need to consider voltage range -Vcc to +2Vcc and hence for the MIN > case the range will be -3.0 to +6.0. So in that case what current > values we need to put for the voltage range -3.3 to -3.0 and +6.0 to > +6.6 whose values will be missing in MIN corner simulations. > > I hope i have explained the problem correctly and let me know your > answers. > > Thanks & Regards > Sudarshan > > > > On 10/18/07, *Mirmak, Michael* > wrote: > > Sudarshan, > > > > Thanks for the message. The major issue appears to be problems in > generating the Vcc-relative information, but some general supply > issues are cropping up too. Assuming this is just a regular I/O > buffer without internal terminations... > > > > 1) I would expect the Pullup I-V tables to pass through the zero V, > zero I axis intercept. Yet they do not, with the max and min data > shifted by ~0.3 V above and below 0 V, respectively. This suggests > that the math used to generate the tables may be incorrect. Remember > that, if the data at Vout is collected ground-relative, you can make > the power clamp and pullup table data in Vcc-relative by the formula > (Vtable_corner = Vcc_corner - Vout_corner), where xxx_corner refers to > a value collected for typ, min or max. For example, if Vcc_min is 4.5 > V, data collected ground-relative for 0.0 at the output would be > entered in the table for the 4.5 V row. > > > > The supply voltages and the Pullup I-V axis intercepts (when plotted > ground-relative) don't agree, which implies a problem with the supply > listed for the [Voltage Range] keyword not matching either the real > circuit or the values used to generate the Vcc-relative tables. > > > > 2) The voltage for the buffer is 5 V +/- 0.5, but the V-t fixture is > 3.3 V +/- 0.3 V. This complicates the math (it gets very hard for me > to calculate the intercepts if they don't match, at least before my > first cup of coffee), but it also suggests that the buffer V-t and I-V > data sets were collected using different settings or otherwise using > different conditions. I would recommend checking the actual fixtures > used for the V-t extraction; matching the fixture voltages to the > voltage supply would make checking easier. > > > > Calculating the right I-V intercepts vs. V-t levels will be easier > once these issues are addressed. > > > > - Michael Mirmak > > Intel Corp. > > Chair, EIA IBIS Open Forum > > > > ------------------------------------------------------------------------ > > *From:* owner-ibis@server.eda.org > [mailto:owner-ibis@server.eda.org ] > *On Behalf Of *Sudarshan H N > *Sent:* Thursday, October 18, 2007 2:16 AM > *To:* ibis@server.eda.org ; > ibis-users@server.eda.org > *Subject:* [IBIS] I-V and V-t curve mismatch > > Hello Experts, > > I am finding problem with one of my IBIS model in I-V and V-t curve > mismatch. Please find the attached model for the refernence. > > ERROR - Model dummy: The [Rising Waveform] > with [R_fixture]=80 Ohms and [V_fixture]=0V > has TYP column DC endpoints of 0.01V and 2.66v, but > an equivalent load applied to the model's I-V tables yields > different voltages (-0.00V and 3.90V), > a difference of 0.25% and 31.85%, respectively. > > I wrote a new tool to generate IBIS models and i am not able to make > out where it is going wrong. > I actually tried to manually calculate the currents at the points , > that it has reported in the above error. > > As it is a rising waveform having a R_fixture to ground the current > at 2.66v (steady state) would be 2.66v/50 = 33.25mA. > > I looked at the voltage corresponding to 33.25mA in pullup table and i > found it is coming around 0.66v. There is a mismatch in the way i am > caluculating also. But i observed a different voltage of 0.66v > compared to what ibischk4 has reported i.e, 3.9v. > > Let me know is the way i am cross checking is correct or not ? If not > let me know the exact procedure. > > Also let me know what might have been gone wrong in the curves. From > the shape of the curves i am not seeing any problem with the way i > have generated. > > Please let me know your answers as soon as possible. > > Note : Please dont consider any other values apart from the curves > like Ramp , C_comp etc as i have dummy values for these place holders. > > Thanks & Regards > Sudarshan > > -- > 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. ** > > * > -- > 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. * - -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. - --------------000806080808010904070500 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit To follow up with what Tom and Todd have said, modern process technology often will not tolerate voltage swings 1 X Vdd beyond the rails, like older technologies did. In many cases, you will need to adjust your extraction method so that it does not exceed the device breakdown limits, either in Spice or in measurement-based extraction.

Scott McMorrow Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 (401) 284-1827 Business (401) 284-1840 Fax http://www.teraspeed.com Teraspeed® is the registered service mark of Teraspeed Consulting Group LLC

Todd Westerhoff wrote:

I agree with Tom.

The choice of -2*VDD to 2*VDD is somewhat arbitrary … it’s simply meant to ensure that you have valid V/I data for any voltage that the part will be exposed to. Thus, you don’t need to adjust the voltage ranges based on the MIN and MAX cases. For most technologies, if you have overshoot that’s equal to the supply voltage, you have bigger problems than model accuracy !

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

From: owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf Of Tom Dagostino
Sent: Monday, October 22, 2007 12:11 PM
To: 'Sudarshan H N'; 'Mirmak, Michael'
Cc: ibis@eda.org; ibis-users@eda.org
Subject: RE: [IBIS] I-V and V-t curve mismatch

Model all three corners from –Vdd to 2*Vdd where Vdd is the typical voltage.

Tom Dagostino
Teraspeed(R) Labs
13610 SW Harness Lane
Beaverton, OR 97008
503-430-1065
tom@teraspeed.com
www.teraspeed.com

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

From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On Behalf Of Sudarshan H N
Sent: Monday, October 22, 2007 7:43 AM
To: Mirmak, Michael
Cc: ibis@server.eda.org; ibis-users@server.eda.org
Subject: Re: [IBIS] I-V and V-t curve mismatch

Hi Michael & All,

Can you people answer to my question regarding the voltage ranges in MIN and MAX case as explained below. As Arpad mentioned in one of the earlier mails the range for MIN and MAX case is

typ: -3.3 to 6.6

min: -3.6 to 6.3

max: -3.0 to 6.9

How do we select this range for MIN and MAX case. Is there any document which explains the selection criteria for these corners ? If there is no logic , then how can we decide if the supply is 1.8 V supply or 2.5V supply?

Let me know your answers.

Regards
Sudarshan

On 10/19/07, Sudarshan H N < hn.sudarshan@gmail.com> wrote:

Hi Michael,

Thanks for your detailed reponse. I made a small mistake in putting the voltage ranges as you mentioned. As i was writing a new tool , at this point of time i didnt give much attention to printing correct voltage range , and i was only worried about the correct extraction of V-t and I-V tables.

I have considered the formula you have mentioned for calculating Vcc-relative Pullup and Powerclamp tables. I changed the voltage range to (3.3, 3.0 and 3.6 which is the actual case) and now i am able to get rid of all these errors.

But still i have one query regarding the values for I-V curves when it is in the Min or MAX corner. I asked about this in my previous mail. Lynne and Arpad gave some answers but that didnt solve my problem.

The problem with MIN and MAX corner is , what is the voltage range we need to consider for MIN and MAX case . For example if we consider 3.3 V supply, the typical range would be -3.3 to 6.6 and this is the voltage range in the IBIS file for all 3 corners. As per the cookbook we need to consider voltage range - -Vcc to +2Vcc and hence for the MIN case the range will be -3.0 to +6.0. So in that case what current values we need to put for the voltage range -3.3 to -3.0 and +6.0 to +6.6 whose values will be missing in MIN corner simulations.

I hope i have explained the problem correctly and let me know your answers.

Thanks & Regards
Sudarshan

On 10/18/07, Mirmak, Michael <michael.mirmak@intel.com > wrote:

Sudarshan,

Thanks for the message. The major issue appears to be problems in generating the Vcc-relative information, but some general supply issues are cropping up too. Assuming this is just a regular I/O buffer without internal terminations...

1) I would expect the Pullup I-V tables to pass through the zero V, zero I axis intercept. Yet they do not, with the max and min data shifted by ~0.3 V above and below 0 V, respectively. This suggests that the math used to generate the tables may be incorrect. Remember that, if the data at Vout is collected ground-relative, you can make the power clamp and pullup table data in Vcc-relative by the formula (Vtable_corner = Vcc_corner - Vout_corner), where xxx_corner refers to a value collected for typ, min or max. For example, if Vcc_min is 4.5 V, data collected ground-relative for 0.0 at the output would be entered in the table for the 4.5 V row.

The supply voltages and the Pullup I-V axis intercepts (when plotted ground-relative) don't agree, which implies a problem with the supply listed for the [Voltage Range] keyword not matching either the real circuit or the values used to generate the Vcc-relative tables.

2) The voltage for the buffer is 5 V +/- 0.5, but the V-t fixture is 3.3 V +/- 0.3 V. This complicates the math (it gets very hard for me to calculate the intercepts if they don't match, at least before my first cup of coffee), but it also suggests that the buffer V-t and I-V data sets were collected using different settings or otherwise using different conditions. I would recommend checking the actual fixtures used for the V-t extraction; matching the fixture voltages to the voltage supply would make checking easier.

Calculating the right I-V intercepts vs. V-t levels will be easier once these issues are addressed.

- Michael Mirmak

Intel Corp.

Chair, EIA IBIS Open Forum

From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On Behalf Of Sudarshan H N
Sent: Thursday, October 18, 2007 2:16 AM
To: ibis@server.eda.org; ibis-users@server.eda.org
Subject: [IBIS] I-V and V-t curve mismatch

Hello Experts,

I am finding problem with one of my IBIS model in I-V and V-t curve mismatch. Please find the attached model for the refernence.

ERROR - Model dummy: The [Rising Waveform]
      with [R_fixture]=80 Ohms and [V_fixture]=0V
      has TYP column DC endpoints of 0.01V and 2.66v, but
      an equivalent load applied to the model's I-V tables yields
      different voltages (-0.00V and 3.90V),
      a difference of 0.25% and 31.85%, respectively.

I wrote a new tool to generate IBIS models and i am not able to make out where it is going wrong.
I actually tried to manually calculate the currents at the points , that it has reported in the above error.

As it is a rising waveform having a R_fixture to ground the current at 2.66v (steady state) would be 2.66v/50 = 33.25mA.

I looked at the voltage corresponding to 33.25mA in pullup table and i found it is coming around 0.66v. There is a mismatch in the way i am caluculating also. But i observed a different voltage of 0.66v compared to what ibischk4 has reported i.e, 3.9v.

Let me know is the way i am cross checking is correct or not ? If not let me know the exact procedure.

Also let me know what might have been gone wrong in the curves. From the shape of the curves i am not seeing any problem with the way i have generated.

Please let me know your answers as soon as possible.

Note : Please dont consider any other values apart from the curves like Ramp , C_comp etc as i have dummy values for these place holders.

Thanks & Regards
Sudarshan

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This message has been scanned for viruses and
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believed to be clean. - --------------000806080808010904070500-- - -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail majordomo@eda-stds.org |with the appropriate command message(s) in the body: | | help | subscribe ibis | subscribe ibis-users | unsubscribe ibis | unsubscribe ibis-users | |or e-mail a request to ibis-request@eda-stds.org. | |IBIS reflector archives exist under: | | http://www.eda-stds.org/pub/ibis/email_archive/ Recent | http://www.eda-stds.org/pub/ibis/users_archive/ Recent | http://www.eda-stds.org/pub/ibis/email/ E-mail since 1993 ------------------------------ Date: Mon, 22 Oct 2007 11:01:22 -0700 From: "Muranyi, Arpad" Subject: RE: [IBIS-Users] RE: [IBIS] I-V and V-t curve mismatch This is a multi-part message in MIME format. - ------_=_NextPart_001_01C814D5.8FC42024 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable While both Tom and Todd are suggesting the right thing, I think both need some correction, or clarification... =20 Todd wrote "-2*VDD to 2*VDD" in which the first -2*VDD should have read -VDD. =20 Tom's comment about using typical VDD is correct for the range calculation but you need to be careful an not apply that suggestion to the VDD of the power you apply to the device under test and the VDD-relative calculations (in case you don't measure it VDD relative directly). =20 So to sum it up, my numbers in my first reply were calculated as follows: =20 For the pulldown the sweep range is always: - -VDD_typ to 2*VDD_typ =3D -3.3 to 6.6, regardless of which case you are generating, i.e. whether the supply voltage to the chip=20 is typ=3D3.3, min=3D3.0, or max=3D3.6 volts (assuming that the chip's pulldown is connected to GND or 0 volts). =20 For the pullup, which is swept VDD relative, the numbers for the sweep ranges in GND relative orientation will work out this way: =20 - -VDD_typ to 2*VDD_typ with respect to VDD_typ =3D 6.6 to -3.3 - -VDD_typ to 2*VDD_typ with respect to VDD_min =3D 6.3 to -3.6 - -VDD_typ to 2*VDD_typ with respect to VDD_max =3D 6.9 to -3.0 =20 Note that this numbers are only this confusing because you are looking at the sweep ranges in a GND relative way, while you are really doing the same rule as above for the pulldown with respect to VDD. =20 Of course the direction of the sweep is irrelevant, as long as the device doesn't act up. Some times devices can do funny things depending on which direction you do the sweep. Also, to help the simulator to find an operating point I suggest that you start the seep at the same rail voltage the device is driving to (i.e. VDD for logic high or GND for logic low) and then do the sweep you need for the IBIS model. There is a better chance to get the simulator converge that way... =20 I hope this helps, =20 Arpad =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D ________________________________ From: owner-ibis-users@server.eda.org [mailto:owner-ibis-users@server.eda.org] On Behalf Of Todd Westerhoff Sent: Monday, October 22, 2007 10:09 AM To: ibis@server.eda.org; ibis-users@server.eda.org Cc: tom@teraspeed.com Subject: [IBIS-Users] RE: [IBIS] I-V and V-t curve mismatch I agree with Tom. =20 The choice of -2*VDD to 2*VDD is somewhat arbitrary ... it's simply meant to ensure that you have valid V/I data for any voltage that the part will be exposed to. Thus, you don't need to adjust the voltage ranges based on the MIN and MAX cases. For most technologies, if you have overshoot that's equal to the supply voltage, you have bigger problems than model accuracy ! =20 Todd. =20 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 ________________________________ From: owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf Of Tom Dagostino Sent: Monday, October 22, 2007 12:11 PM To: 'Sudarshan H N'; 'Mirmak, Michael' Cc: ibis@eda.org; ibis-users@eda.org Subject: RE: [IBIS] I-V and V-t curve mismatch =20 Model all three corners from -Vdd to 2*Vdd where Vdd is the typical voltage. =20 Tom Dagostino Teraspeed(R) Labs 13610 SW Harness Lane Beaverton, OR 97008 503-430-1065 tom@teraspeed.com www.teraspeed.com Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 401-284-1827=20 From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On Behalf Of Sudarshan H N Sent: Monday, October 22, 2007 7:43 AM To: Mirmak, Michael Cc: ibis@server.eda.org; ibis-users@server.eda.org Subject: Re: [IBIS] I-V and V-t curve mismatch =20 Hi Michael & All, Can you people answer to my question regarding the voltage ranges in MIN and MAX case as explained below. As Arpad mentioned in one of the earlier mails the range for MIN and MAX case is typ: -3.3 to 6.6 min: -3.6 to 6.3 max: -3.0 to 6.9 How do we select this range for MIN and MAX case. Is there any document which explains the selection criteria for these corners ? If there is no logic , then how can we decide if the supply is 1.8 V supply or 2.5V supply? Let me know your answers. Regards Sudarshan =20 On 10/19/07, Sudarshan H N < hn.sudarshan@gmail.com> wrote: Hi Michael,=20 Thanks for your detailed reponse. I made a small mistake in putting the voltage ranges as you mentioned. As i was writing a new tool , at this point of time i didnt give much attention to printing correct voltage range , and i was only worried about the correct extraction of V-t and I-V tables. I have considered the formula you have mentioned for calculating Vcc-relative Pullup and Powerclamp tables. I changed the voltage range to (3.3, 3.0 and 3.6 which is the actual case) and now i am able to get rid of all these errors. But still i have one query regarding the values for I-V curves when it is in the Min or MAX corner. I asked about this in my previous mail. Lynne and Arpad gave some answers but that didnt solve my problem. The problem with MIN and MAX corner is , what is the voltage range we need to consider for MIN and MAX case . For example if we consider 3.3 V supply, the typical range would be -3.3 to 6.6 and this is the voltage range in the IBIS file for all 3 corners. As per the cookbook we need to consider voltage range -Vcc to +2Vcc and hence for the MIN case the range will be -3.0 to +6.0. So in that case what current values we need to put for the voltage range -3.3 to -3.0 and +6.0 to +6.6 whose values will be missing in MIN corner simulations. I hope i have explained the problem correctly and let me know your answers. Thanks & Regards Sudarshan =20 On 10/18/07, Mirmak, Michael wrote: Sudarshan, =20 Thanks for the message. The major issue appears to be problems in generating the Vcc-relative information, but some general supply issues are cropping up too. Assuming this is just a regular I/O buffer without internal terminations... =20 1) I would expect the Pullup I-V tables to pass through the zero V, zero I axis intercept. Yet they do not, with the max and min data shifted by ~0.3 V above and below 0 V, respectively. This suggests that the math used to generate the tables may be incorrect. Remember that, if the data at Vout is collected ground-relative, you can make the power clamp and pullup table data in Vcc-relative by the formula (Vtable_corner =3D Vcc_corner - Vout_corner), where xxx_corner refers to a value collected for typ, min or max. For example, if Vcc_min is 4.5 V, data collected ground-relative for 0.0 at the output would be entered in the table for the 4.5 V row. =20 The supply voltages and the Pullup I-V axis intercepts (when plotted ground-relative) don't agree, which implies a problem with the supply listed for the [Voltage Range] keyword not matching either the real circuit or the values used to generate the Vcc-relative tables. =20 2) The voltage for the buffer is 5 V +/- 0.5, but the V-t fixture is 3.3 V +/- 0.3 V. This complicates the math (it gets very hard for me to calculate the intercepts if they don't match, at least before my first cup of coffee), but it also suggests that the buffer V-t and I-V data sets were collected using different settings or otherwise using different conditions. I would recommend checking the actual fixtures used for the V-t extraction; matching the fixture voltages to the voltage supply would make checking easier. =20 Calculating the right I-V intercepts vs. V-t levels will be easier once these issues are addressed. =20 - - Michael Mirmak Intel Corp. Chair, EIA IBIS Open Forum =20 ________________________________ From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On Behalf Of Sudarshan H N Sent: Thursday, October 18, 2007 2:16 AM To: ibis@server.eda.org; ibis-users@server.eda.org Subject: [IBIS] I-V and V-t curve mismatch Hello Experts, I am finding problem with one of my IBIS model in I-V and V-t curve mismatch. Please find the attached model for the refernence. ERROR - Model dummy: The [Rising Waveform] with [R_fixture]=3D80 Ohms and [V_fixture]=3D0V has TYP column DC endpoints of 0.01V and 2.66v, but an equivalent load applied to the model's I-V tables yields different voltages (-0.00V and 3.90V), a difference of 0.25% and 31.85%, respectively. I wrote a new tool to generate IBIS models and i am not able to make out where it is going wrong. I actually tried to manually calculate the currents at the points , that it has reported in the above error. As it is a rising waveform having a R_fixture to ground the current at 2.66v (steady state) would be 2.66v/50 =3D 33.25mA. I looked at the voltage corresponding to 33.25mA in pullup table and i found it is coming around 0.66v. There is a mismatch in the way i am caluculating also. But i observed a different voltage of 0.66v compared to what ibischk4 has reported i.e, 3.9v.=20 Let me know is the way i am cross checking is correct or not ? If not let me know the exact procedure. Also let me know what might have been gone wrong in the curves. From the shape of the curves i am not seeing any problem with the way i have generated.=20 Please let me know your answers as soon as possible. Note : Please dont consider any other values apart from the curves like Ramp , C_comp etc as i have dummy values for these place holders. Thanks & Regards Sudarshan - --=20 This message has been scanned for viruses and=20 dangerous content by MailScanner, and is=20 believed to be clean.=20 =20 - --=20 This message has been scanned for viruses and=20 dangerous content by MailScanner , and is believed to be clean.=20 - --=20 This message has been scanned for viruses and=20 dangerous content by MailScanner, and is=20 believed to be clean.=20 - --=20 This message has been scanned for viruses and=20 dangerous content by MailScanner , and is believed to be clean.=20 - --=20 This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. - ------_=_NextPart_001_01C814D5.8FC42024 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable
While both Tom and Todd are suggesting the right=20 thing,

I think both need some correction, or=20 clarification...

Todd wrote "-2*VDD to 2*VDD" in which the first=20 - -2*VDD

should have read -VDD.

Tom's comment about using typical VDD is correct for=20 the

range calculation but you need to be careful an not<= /DIV>

apply that suggestion to the VDD of the power you

apply to the device under test and the VDD-relative<= /DIV>
calculations (in case you don't measure it VDD=20 relative

directly).

So to sum it up, my numbers in my first reply were
calculated as follows:

For the pulldown the sweep range is always:

-VDD_typ to 2*VDD_typ =3D -3.3 to 6.6,
regardless of which case you are generating,

i.e. whether the supply voltage to the chip

is typ=3D3.3, min=3D3.0, or max=3D3.6 volts (assuming

that the chip's pulldown is connected to GND

or 0 volts).

For the pullup, which is swept VDD relative,

the numbers for the sweep ranges in GND relative
orientation will work out this way:

-VDD_typ to 2*VDD_typ with respect to VDD_typ =3D 6.6 to= =20 - -3.3

-VDD_typ to= =20 2*VDD_typ with respect to VDD_min =3D 6.3 to -3.6

-VDD_typ to= =20 2*VDD_typ with respect to VDD_max =3D 6.9 to -3.0

Note that this numbers are only this confusing=20 because

you are looking at the sweep ranges in a GND relative

way, while you are really doing the same rule as=20 above

for the pulldown with respect to VDD.

Of course the direction of the sweep is irrelevant,=20 as

long as the device doesn't act up. Some times=20 devices

can do funny things depending on which direction you=

do the sweep. Also, to help the simulator to find=20 an

operating point I suggest that you start the seep at=

the same rail voltage the device is driving to (i.e.=

VDD for logic high or GND for logic low) and then do=

the sweep you need for the IBIS model. There is=20 a

better chance to get the simulator converge that=20 way...

I hope this helps,

Arpad

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

From:=20 owner-ibis-users@server.eda.org [mailto:owner-ibis-users@server.eda.org] On=20 Behalf Of Todd Westerhoff
Sent: Monday, October 22, 2007 10:0= 9=20 AM
To: ibis@server.eda.org; ibis-users@server.eda.org
Cc:=20 tom@teraspeed.com
Subject: [IBIS-Users] RE: [IBIS] I-V and V-t cu= rve=20 mismatch

I agree with=20 Tom.

The choice of -2= *VDD to=20 2*VDD is somewhat arbitrary … it’s simply meant to ensure that = you have valid=20 V/I data for any voltage that the part will be exposed to. Thus, you = don’t=20 need to adjust the voltage ranges based on the MIN and MAX cases. For= most=20 technologies, if you have overshoot that’s equal to the supply voltag= e, you have=20 bigger problems than model accuracy !

Todd.=

Todd=20 Westerhoff
VP, Software Products
SiSoft
6 Clock Tower Place, Suite=20 250
Maynard, MA=20 01754
(978) 461= - -0449=20 x24
twesterh@sisoft.com
www.sisoft.com<= /P>

From:=20 owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf Of Tom Dagostino
Sent: Monday, October 22, 2007 12:11= =20 PM
To: 'Sudarshan H N';= =20 'Mirmak, Michael'
Cc:=20 ibis@eda.org; ibis-users@eda.org
Subject: RE: [IBIS] I-V and V-t curv= e=20 mismatch

Model all t= hree=20 corners from –Vdd to 2*Vdd where Vdd is the typical=20 voltage.

=

Tom Dagostino
Teraspeed(R)=20 Labs
13610 SW Harness= =20 Lane
Beaverton, OR=20 97008
503-430-1065
tom@teras= peed.com
www.teraspeed.com

Teraspeed=20 Consulting Group LLC
12= 1 North=20 River Drive
Narragansett, RI= =20 02882
401-284-1827 =

From:=20 owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On Behalf Of Sudarshan H N
Sent: Monday, October 22, 2007 7:43= =20 AM
To: Mirmak,=20 Michael
Cc:=20 ibis@server.eda.org; ibis-users@server.eda.org
Subject: Re: [IBIS] I-V and V-t curv= e=20 mismatch

Hi Michael & All,

Can y= ou people=20 answer to my question regarding the voltage ranges in MIN and MAX case as= =20 explained below. As Arpad mentioned in one of the earlier mails the range f= or=20 MIN and MAX case is

typ: -3.3 to=20 6.6

min: -3.6 to=20 6.3

max:&n= bsp; -3.0=20 to 6.9

How do we select this range for MIN and MAX cas= e. Is=20 there any document which explains the selection criteria for these corners = ? If=20 there is no logic , then how can we decide if the supply is 1.8 V supply or= 2.5V=20 supply?

Let me know your=20 answers.

Regards
Sudarshan

On 10/19/07, Sudarshan H N < hn.sudarshan@gmail.com>=20 wrote:

Hi Michael,

Thanks for your detailed repo= nse. I=20 made a small mistake in putting the voltage ranges as you mentioned. As i w= as=20 writing a new tool , at this point of time i didnt give much attentio= n to=20 printing correct voltage range , and i was only worried about the correct= =20 extraction of V-t and I-V tables.

I have considered the formula you = have=20 mentioned for calculating Vcc-relative Pullup and Powerclamp tables. I chan= ged=20 the voltage range to (3.3, 3.0 and 3.6 which is the actual case) and now i = am=20 able to get rid of all these errors.

But still i have one query rega= rding=20 the values for I-V curves when it is in the Min or MAX corner. I asked abou= t=20 this in my previous mail. Lynne and Arpad gave some answers but that = didnt=20 solve my problem.

The problem with MIN and MAX corner is , what is t= he=20 voltage range we need to consider for MIN and MAX case . For example if we= =20 consider 3.3 V supply, the typical range would be -3.3 to 6.6 and this is t= he=20 voltage range in the IBIS file for all 3 corners. As per the cookbook we ne= ed to=20 consider voltage range -Vcc to +2Vcc and hence for the MIN case the range w= ill=20 be -3.0 to +6.0. So in that case what current values we need to put for the= =20 voltage range -3.3 to -3.0 and +6.0 to +6.6 whose values will be missing in= MIN=20 corner simulations.

I hope i have explained the problem correctly an= d let=20 me know your answers.

Thanks &=20 Regards
Sudarshan

On 10/18/07, Mirmak, Michael <michael.mirmak@int= el.com=20 > wrote:

Sudarshan,

Thanks for the= =20 message. The major issue appears to be problems in generating the=20 Vcc-relative information, but some general supply issues are cropping up=20 too. Assuming this is just a regular I/O buffer without internal=20 terminations...

1) I would expec= t the=20 Pullup I-V tables to pass through the zero V, zero I axis intercept. = Yet=20 they do not, with the max and min data shifted by ~0.3 V above and below 0 = V,=20 respectively. This suggests that the math used to generate the tables= may=20 be incorrect. Remember that, if the data at Vout is collected=20 ground-relative, you can make the power clamp and pullup table data in=20 Vcc-relative by the formula (Vtable_corner =3D Vcc_corner - Vout_corner), w= here=20 xxx_corner refers to a value collected for typ, min or max. For examp= le,=20 if Vcc_min is 4.5 V, data collected ground-relative for 0.0 at the out= put=20 would be entered in the table for the 4.5 V=20 row.

The supply volta= ges and=20 the Pullup I-V axis intercepts (when plotted ground-relative) don't agree, = which=20 implies a problem with the supply listed for the [Voltage Range] keywo= rd=20 not matching either the real circuit or the values used to generate the=20 Vcc-relative tables.

2) The voltage f= or the=20 buffer is 5 V +/- 0.5, but the V-t fixture is 3.3 V +/- 0.3 V. This= =20 complicates the math (it gets very hard for me to calculate the intercepts = if=20 they don't match, at least before my first cup of coffee), but it also sugg= ests=20 that the buffer V-t and I-V data sets were collected using different settin= gs or=20 otherwise using different conditions. I would recommend checking the= =20 actual fixtures used for the V-t extraction; matching the fixture voltages = to=20 the voltage supply would make checking easier.

Calculating the = right=20 I-V intercepts vs. V-t levels will be easier once these issues are=20 addressed.

- Michael=20 Mirmak

Intel=20 Corp.

Chair, EI= A IBIS=20 Open Forum

From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On Behalf Of Sudarshan H N
Sent: Thursday, October 18, 2007 2:1= 6=20 AM
To: ibis@server.eda.org= ; ibis-users@server.eda.org
Subject: [IBIS] I-V and V-t curve=20 mismatch

Hello Experts,

I am finding= problem=20 with one of my IBIS model in I-V and V-t curve mismatch. Please find the=20 attached model for the refernence.

ERROR - Model dummy: The [Rising= =20 Waveform]
      with [R_fixture]=3D80 Ohms and= =20 [V_fixture]=3D0V
      has TYP column DC endpoi= nts=20 of 0.01V and 2.66v, but
      an=20 equivalent load applied to the model's I-V tables=20 yields
      different voltages (-0.00V and&nbs= p;=20 3.90V),
      a difference of 0.25% and= =20 31.85%, respectively.

I wrote a new tool to generate IBIS models and= i am=20 not able to make out where it is going wrong.
I actually tried to manual= ly=20 calculate the currents at the points , that it has reported in the above=20 error.

As it is a rising waveform having a R_fixture to ground = the=20 current at 2.66v (steady state) would be 2.66v/50 =3D 33.25mA.

I loo= ked at=20 the voltage corresponding to 33.25mA in pullup table and i found it is comi= ng=20 around 0.66v. There is a mismatch in the way i am caluculating also. But i= =20 observed a different voltage of 0.66v compared to what ibischk4 has reporte= d=20 i.e, 3.9v.

Let me know is the way i am cross checking is correct or= not=20 ? If not let me know the exact procedure.

Also let me know wha= t=20 might have been gone wrong in the curves. From the shape of the curves i am= not=20 seeing any problem with the way i have generated.

Please let me kno= w=20 your answers as soon as possible.

Note : Please dont consider any ot= her=20 values apart from the curves like Ramp , C_comp etc as i have dummy values = for=20 these place holders.

Thanks &=20 Regards
Sudarshan

--
This message has been scanned for viruses = and=20
dangerous content by MailScanner,=20 and is
believed to be clean.=20

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