From: owner-ibis-users@eda.org (ibis-users) To: ibis-users-digest@eda.org Subject: ibis-users V1 #175 Reply-To: Sender: owner-ibis-users@eda.org Errors-To: owner-ibis-users@eda.org Precedence: bulk ibis-users Friday, June 10 2011 Volume 01 : Number 175 ---------------------------------------------------------------------- Date: Thu, 2 Jun 2011 06:48:01 -0700 From: "Muranyi, Arpad" Subject: RE: [IBIS-Users] Requesting for some help / information regarding the use of IBIS in SI simulation. This is a multi-part message in MIME format. - ------_=_NextPart_001_01CC212B.B13B969F Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Just a minor correction regarding: =20 =20 =B7 Package model description in IBIS=20 o Allows finer grain description of detailed models =A7 This can be multiple lumped RLC models or multiple Tlines or any combi= nation. =20 =20 The [Package Model] / [Define Package Model] keywords in IBIS allow a single lumped RLC matrix, or a multi-segment T-line modeling approach. =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 =20 =20 From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf = Of Doug Burns Sent: Thursday, June 02, 2011 6:54 AM To: bradb@sigrity.com; 'Scott McMorrow' Cc: 'Ray Anderson'; 'ibis-users' Subject: RE: [IBIS-Users] Requesting for some help / information regarding = the use of IBIS in SI simulation. =20 Brad, =20 I don't think we really disagree, but let us simplify the statements Given the model you have, what would you agree with: =B7 Single RLC Model ala Simple IBIS o This does not model the resonances o This provides a large discontinuity to a high speed edge =B7 Simple Tline model using RLC Characteristics o This does not model resonance o Better match to actual (ie less ringing than Lumped model) =A7 Better does not mean accurate or correct, just closer to the desired t= han a lumped model =B7 Package model description in IBIS=20 o Allows finer grain description of detailed models =A7 This can be multiple lumped RLC models or multiple Tlines or any combi= nation. =A7 In the limit, a Tline segment can be modeled as multiple RLC pieces to= represent a distributed nature o Will model resonances you speak about at least at first order =20 I assume that you will agree with all of the above. =20 Therefore, what I am saying is that interconnect, by its very physical natu= re represents a distributed RLC structure. Modeling any segment that is lon= g compared to the edge rate of the signal is better modeled as a Tline than= a lumped model such that the distributed nature of the segment can be capt= ured.=20 =20 For the example you cite, a simple RLC does not model the behavior and ther= e is no rational to believe just making the model into a tline model would = fix that issues. However, for a multi-segment model using lumped values for= each segment, my experience is that using tline models for all segments th= at have length greater than the 1/3 to 1/2 the rise time (Almost always the= case with high speed signals), that a tline description is better than the= RLC description. This is true even in the multi-segmented implementation= =20 =20 Doug =20 =20 - -----Original Message----- From: Brad Brim [mailto:bradb@sigrity.com]=20 Sent: Thursday, June 02, 2011 5:55 AM To: 'Doug Burns'; 'Scott McMorrow' Cc: 'Ray Anderson'; 'ibis-users' Subject: RE: [IBIS-Users] Requesting for some help / information regarding = the use of IBIS in SI simulation. =20 hi guys, =20 Guess we'll agree to disagree. =20 I have experience with any number of simple packages that violate your "better" supposition for a uniformly distributed TL model. Why would this occur, because I completely agree with you that it is counter intuitive. =20 =46rom a package I recently characterized in some detail for system SI/PI analysis; let's say the net behaves as static RLC to 2Ghz, then at about 4GHz there is some form of resonance in the signals or the planes. There's a suckout in the response and then at higher frequencies it behaves more like the TL you guys propose. If you assume the TL, then you completely miss this behavior, and I do mean "completely". For this DDR bus you probably don't care about the spectrum above 8GHz where it is again more TL like. But you certainly DO care about the spectrum between 2Ghz and 6Ghz where it looks nothing like a TL. If I choose properly a TEE or PI circuit to model the behavior in this mid frequency range (since either works to 2Ghz) then you get a much better transient system-level simulation than using your proposed TL model. This is true even though the TEE/PI response at higher frequencies is much worse than the uniform TL model. There is energy in the mid spectrum but not in the high spectrum for this application. If I use a multi-stage RLC model then select the element values to fit the broadband response then I can get match at both mid and high frequencies to well 10Ghz and make all of us happier (but maybe not to 40GHz). =20 This is NOT a corner case. I see it in many of the package I characterize. If I was trying to do a best fit to 40Ghz for this same package because my signals had energy spread out that broadband, then it would probably be better to use the uniform TL model. However, not all applications call for it and the system is much better characterized with a model more correct where the signals actually have energy. =20 cheers, -Brad=20 =20 > -----Original Message----- > From: Doug Burns [mailto:dburns@sisoft.com]=20 > Sent: Wednesday, June 01, 2011 6:55 AM > To: 'Scott McMorrow'; bradb@sigrity.com > Cc: 'Ray Anderson'; 'ibis-users' > Subject: RE: [IBIS-Users] Requesting for some help /=20 > information regarding the use of IBIS in SI simulation. >=20 > All, >=20 > I have to agree with Scott on this. For the type of packages=20 > as outlined by Scott, if one were to take the detailed model=20 > from a simulator and decompose it to a RLC format, the best=20 > correlation between the detailed model and the simplified=20 > model will occur when the simplified RLC is treated as a=20 > distributed structure such as a transmission line. Like=20 > Scott, we have proven this multiple time on a wide variety of=20 > package styles (leadframe through 24+ layer packages). There=20 > is no disagreement that a detailed model will be better,=20 > especially for high frequencies, but we must work within the=20 > limits of what IBIS can support. The mode detailed that=20 > package description is in IBIS, the better estimation we can=20 > make, but using lumped data for high speed signals is just=20 > causing an issue where one really will not exist. EDA tools=20 > need to make the best estimation of the available data to=20 > predict performance. >=20 > Doug >=20 > Douglas Burns > Signal Integrity Software, Inc > 6 Clock Tower Place > Maynard, MA 01754 > 978-461-0449 x14 >=20 >=20=20 > -----Original Message----- > From: owner-ibis-users@eda.org=20 > [mailto:owner-ibis-users@eda.org] On Behalf Of Scott McMorrow > Sent: Wednesday, June 01, 2011 9:33 AM > To: bradb@sigrity.com > Cc: 'Ray Anderson'; 'ibis-users' > Subject: Re: [IBIS-Users] Requesting for some help /=20 > information regarding the use of IBIS in SI simulation. >=20 > Brad >=20 > It is certainly your prerogative to disagree with me. In the=20 > context of the original question, we are not talking about=20 > randomly distributed RLC, but rather package connections from=20 > board to silicon, which is the case in most IBIS models.=20=20 > Given that, we know the general topology.=20=20 > Whether the package uses lead frame, 2 layer FC packaging,=20 > 2/4 layer organic wire bond packaging, or multilayer buildup=20 > packaging, a single path from die to ball looks remarkably=20 > similar to cascaded transmission lines. Even bond wires look=20 > like transmission lines. >=20 > If I'm given a single RLC for an IBIS model of a=20 > conventionally packaged silicon device , then I can guarantee=20 > you that the simulation will be more faithful to measurements=20 > when the transmission line equivalent is used, rather than=20 > lumped elements. Been there, done the measurements many,=20 > many times. When multiple sections are specified in the IBIS=20 > .pkg format, then there is no ambiguity, a non-zero RLC=20 > section length defines a distributed element, and a zero=20 > length section defines a lumped element. The simulator=20 > should model it as such. >=20 > Having done correlation of package modeling to measurements=20 > from DC to 40 GHz on a 12-layer build-up with near zero=20 > error, I'm well aware of the issues involved with using the=20 > wrong modeling method, and poor material modeling. I agree=20 > with you that a single RLC is an extremely poor approximation=20 > of any complex package interconnect, or any interconnect for=20 > that matter. However, given that a user is presented with an=20 > RLC that was extracted with a quasi-static solver, as is the=20 > case with most IBIS models, I maintain that the result will=20 > be closer to reality when transformed into the distributed=20 > transmission line equivalent. I've seen way too many cases=20 > where simulators used a lumped RLC directly, grossly over=20 > predicting ringing at the die and in the channel, and=20 > confirmed by physical measurements. >=20 > When we get into full-wave and hybrid full-wave AC modeling=20 > of packages there are a host of other issues that we can=20 > discuss, such as accurate dielectric modeling, accurate=20 > surface roughness modeling, as-designed vs. as-built package=20 > geometries, +/- 15% impedance variation due to manufacturing=20 > process and electromagnetic non-locality. But that is for=20 > another time. >=20 >=20 > best regards, >=20 > Scott >=20 >=20 > Scott McMorrow > Teraspeed Consulting Group LLC > 121 North River Drive > Narragansett, RI 02882 > (401) 284-1827 Business > (401) 284-1840 Fax >=20 > http://www.teraspeed.com >=20 > TeraspeedR is the registered service mark of Teraspeed=20 > Consulting Group LLC >=20 >=20 > On 6/1/2011 1:53 AM, Brad Brim wrote: > > hello Scott, > > > > I don't agree with you. Such simulators (or model extractors which=20 > > write > out > > such "postprocessed" model data) are no more assured accurate than > simply > > applying or writing out the base RLC data. > > > > Most package extractors, especially ones you may refer to as=20 > > applicable "from the beginning", are based on static RLC=20 > simulation in=20 > > which a > single L > > and C are extracted at exactly DC from two distinct simulations;=20 > > magnetostatic and electrostatic respectively. One has NO CLUE how to > form > > the equivalent circuit given only the static lumped L and C=20 > computed=20 > > independently. Of course, as asked and discussed by Ray, if=20 > the user=20 > > has insight from the physical structure then a more broadband model=20 > > MIGHT be generated, but there is no guarantee! > > One person assuming a PI circuit (with the C split equally=20 > in half -=20 > > or > even > > unequally - and the L in the middle) and another person=20 > assuming a TEE=20 > > circuit (with the L split and the shunt C in the middle) are no more > correct > > than the other. One has NO IDEA of the high frequency=20 > behavior of the=20 > > circuit (either just above the quasistatic limit where the likely > spectral > > content is relevant or higher where it is less likely relevant)=20 > > without > some > > form of AC high-frequency simulation or measurement. The=20 > behavior at=20 > > "infinite" frequency in meaningless and to argue that a uniformly=20 > > distributed multi-stage ladder network is valid has no more > justification > > than another person arguing it should me a lowpass network with all=20 > > the inductance on the die side because of wirebond inductance. This=20 > > argument > has > > blindly been accepted and argued for many years. It has been=20 > > unjustified > and > > wrong, as you would say, "from the beginning". > > > > Want a valid model at higher frequencies, then extract AC=20 > information > from > > which to generate it. One's guess or intuitive argument without AC=20 > > information to back it up is only a guess, as Andy stated. The=20 > > classical uniformly distributed ladder network is a=20 > deceptively simple=20 > > and > intuitively > > pleasing assumption that is easy to understand and unfortunately > accepted by > > way too many people in the industry. This supposed more=20 > accurate guess > has > > failed in too many cases and can even be worse than a=20 > simple totally=20 > > unbalanced low pass filter assumption over the frequency=20 > spectrum of=20 > > relevance. > > > > Many commercially available RLC extractors continue to make this > assumption > > today. Users are placed at significant risk because they falsely=20 > > believe > the > > model is in some sense "broadband" or "wideband". It is a=20 > guess with=20 > > no guarantee to be any better than any other assumed more=20 > distributed=20 > > equivalent circuit for which there is no theoretical or physical=20 > > justification. > > > > If one starts with AC data, assumes an equivalent circuit and *then* > selects > > element values in such to fit the data then there is reason to argue > this is > > a more valid model at higher frequencies. One cannot do=20 > this from only > DC > > terminal-based data. Not that it's difficult, it is impossible. > > > > best regards, > > -Brad > > > > > >> -----Original Message----- > >> From: owner-ibis-users@eda.org > >> [mailto:owner-ibis-users@eda.org] On Behalf Of Scott McMorrow > >> Sent: Tuesday, May 31, 2011 5:04 PM > >> To: Ray Anderson > >> Cc: ibis-users; Ray Anderson > >> Subject: Re: [IBIS-Users] Requesting for some help / information=20 > >> regarding the use of IBIS in SI simulation. > >> > >> Since the beginning of IBIS, the most accurate simulators=20 > would turn=20 > >> the RLC package parasitics into a transmission line=20 > equivalent. In=20 > >> lieu of any additional information it is the most=20 > reasonable thing to=20 > >> do, since packages can be approximated as transmission lines. > >> > >> > >> 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 > >> > >> TeraspeedR is the registered service mark of Teraspeed Consulting=20 > >> Group LLC > >> > >> > >> On 5/31/2011 7:59 PM, Ray Anderson wrote: > >>> If you are using extracted RLC data to manually set up=20 > the package=20 > >>> model you can certainly make intelligent decisions on the > >> topology of > >>> the model and the distribution of the RLC parasitics. > >> However if you > >>> are depending on a simulator to read the data from a IBIS > >> .pkg format > >>> file (or the [PIN] data) and set up a model for you then > >> your results > >>> may differ from simulator to simulator. > >>> > >>> -Ray > >>> Xilinx Inc. > >>> > >>> > >>> -----Original Message----- > >>> From: owner-ibis-users@eda.org=20 > [mailto:owner-ibis-users@eda.org] On=20 > >>> Behalf Of Andrew Ingraham > >>> Sent: Tuesday, May 31, 2011 4:48 PM > >>> To: ibis-users > >>> Subject: Re: [IBIS-Users] Requesting for some help / information=20 > >>> regarding the use of IBIS in SI simulation. > >>> > >>> Yes. > >>> > >>> I am usually tempted to start with an evenly distributed > >> RLC model ... > >>> unless I have reason to think that the distribution is > >> otherwise. For > >>> example, wirebonds might have most of the inductance and > >> resistance, > >>> whereas the leadframe may have more capacitance, which > >> might influence > >>> one to imbalance those factors unequally between die end > >> and pin end. > >>> But without hard data to back it up, that is just guessing. > >>> > >>> Andy > >>> > >> -- > >> This message has been scanned for viruses and dangerous content by=20 > >> MailScanner, and is believed to be clean. > >> > >>=20 > -------------------------------------------------------------------- > >> |For help or to subscribe/unsubscribe, e-mail=20 > majordomo@eda-stds.org=20 > >> |with the appropriate command message(s) in the body: > >> | > >> | help > >> | subscribe ibis > >> | subscribe ibis-users > >> | unsubscribe ibis=20=20 > >> | 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=20 > >> | http://www.eda-stds.org/pub/ibis/users_archive/ Recent > >> | http://www.eda-stds.org/pub/ibis/email/ E-mail=20 > since 1993 > >> >=20 > -- > This message has been scanned for viruses and dangerous=20 > content by MailScanner, and is believed to be clean. >=20 > -------------------------------------------------------------------- > |For help or to subscribe/unsubscribe, e-mail majordomo@eda-stds.org=20 > |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=20=20 > | http://www.eda-stds.org/pub/ibis/users_archive/ Recent > | http://www.eda-stds.org/pub/ibis/email/ E-mail since 1993 >=20 =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 dangerous content by MailScanner, and is believed to be clean. - ------_=_NextPart_001_01CC212B.B13B969F Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Just a minor correct= ion regarding:

 

 

=B7   &= nbsp;     Package model = description in IBIS

o    Allows finer grain descripti= on of detailed models

=A7=   This can be multiple lumped RLC models or multiple Tlines or any co= mbination.

 

 

The [Package Model= ] / [Define Package Model] keywords in

T-line modeling approach.

 

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

 

 <= /o:p>

From: owner-ibis-users@e= da.org [mailto:owner-ibis-users@eda.org] On Behalf Of Doug Burns
= Sent: Thursday, June 02, 2011 6:54 AM
To: bradb@sigrity.co= m; 'Scott McMorrow'
Cc: 'Ray Anderson'; 'ibis-users'
Subjec= t: RE: [IBIS-Users] Requesting for some help / information regarding th= e use of IBIS in SI simulation.

 

Brad,<= /p>

 

&nb= sp;I don't think we really disagree, but let us simplify the statements

 Given the model you have, what wou= ld you agree with:

=B7      &= nbsp;  Single RLC Model ala Simple IBIS=

o  &nbs= p; This does not model the resonances

o=     This provides a large discontinuity to a high speed edge<= /o:p>

=B7         Simple Tline model using RLC Characteristics<= /p>

o    This does not model resonance

o    Bett= er match to actual (ie less ringing than Lumped model)

=A7&= nbsp;        Package model description in IBIS

o    Allows fin= er grain description of detailed models

<= ![if !supportLists]>=A7  This can be multiple lumped RLC models or multipl= e Tlines or any combination.

=A7  In the limit, a Tline segment can be modeled as multiple RLC= pieces to represent a distributed nature

o    Will mo= del resonances you speak about at least at first order

 

I assume tha= t you will agree with all of the above.

 

Therefore, what I am saying= is that interconnect, by its very physical nature represents a distributed= RLC structure. Modeling any segment that is long compared to the edge rate= of the signal is better modeled as a Tline than a lumped model such that t= he distributed nature of the segment can be captured.

 

For the exam= ple you cite, a simple RLC does not model the behavior and there is no rati= onal to believe just making the model into a tline model would fix that iss= ues. However, for a multi-segment model using lumped values for each segmen= t, my experience is that using tline models for all segments that have leng= th greater than the 1/3 to 1/2 the rise time (Almost always the case with h= igh speed signals), that a tline description is better than the RLC descrip= tion. This is true even in the multi-segmented implementation

 

&nbs= p;Doug

 

 

-----Original = Message-----
From: Brad Brim [mailto:bradb@sigrity.com]
Sent: Thursd= ay, June 02, 2011 5:55 AM
To: 'Doug Burns'; 'Scott McMorrow'
Cc: 'Ray= Anderson'; 'ibis-users'
Subject: RE: [IBIS-Users] Requesting for some h= elp / information regarding the use of IBIS in SI simulation.

 

hi gu= ys,

 

Guess we'll agree to disagree.

 

I have experience with a= ny number of simple packages that violate your

"better" supposition for a uniformly distributed TL mod= el. Why would this

occur, because I c= ompletely agree with you that it is counter intuitive.

 

From a packa= ge I recently characterized in some detail for system SI/PI

<= p class=3DMsoPlainText>analysis; let's say the net behaves as static RLC to= 2Ghz, then at about

4GHz there is so= me form of resonance in the signals or the planes. There's a

=

suckout in the response and then at higher frequenc= ies it behaves more like

the TL you g= uys propose. If you assume the TL, then you completely miss this=

behavior, and I do mean "completely".= For this DDR bus you probably don't

= care about the spectrum above 8GHz where it is again more TL like. But you<= o:p>

certainly DO care about the spectrum = between 2Ghz and 6Ghz where it looks

= nothing like a TL. If I choose properly a TEE or PI circuit to model the

behavior in this mid frequency range (s= ince either works to 2Ghz) then you

g= et a much better transient system-level simulation than using your proposed=

TL model. This is true even though t= he TEE/PI response at higher frequencies

is much worse than the uniform TL model. There is energy in the mid spe= ctrum

but not in the high spectrum fo= r this application. If I use a multi-stage

RLC model then select the element values to fit the broadband respons= e then

I can get match at both mid an= d high frequencies to well 10Ghz and make all

of us happier (but maybe not to 40GHz).

 

This is NOT a corn= er case. I see it in many of the package I characterize.

If I was trying to do a best fit to 40Ghz for this same= package because my

signals had energ= y spread out that broadband, then it would probably be

better to use the uniform TL model. However, not all appl= ications call for

it and the system i= s much better characterized with a model more correct

where the signals actually have energy.

 

cheers,

 -Brad

 

> -----Original= Message-----

> From: Doug Burns [= mailto:dburns@sisoft.com]

> Sent:= Wednesday, June 01, 2011 6:55 AM

>= ; To: 'Scott McMorrow'; bradb@sigrity.com

> Cc: 'Ray Anderson'; 'ibis-users'

> Subject: RE: [IBIS-Users] Requesting for some help / =

> information regarding the use of IBIS in S= I simulation.

>

> All,

> <= o:p>

>  I have to agree with Scott= on this. For the type of packages

&= gt; as outlined by Scott, if one were to take the detailed model

> from a simulator and decompose it to a RL= C format, the best

> correlation = between the detailed model and the simplified

> model will occur when the simplified RLC is treated as a

> distributed structure such as a tr= ansmission line. Like

> Scott, we= have proven this multiple time on a wide variety of

> package styles (leadframe through 24+ layer packages)= . There

> is no disagreement that= a detailed model will be better,

&g= t; especially for high frequencies, but we must work within the =

> limits of what IBIS can support. The mode = detailed that

> package descripti= on is in IBIS, the better estimation we can

> make, but using lumped data for high speed signals is just

> causing an issue where one really = will not exist. EDA tools

> need = to make the best estimation of the available data to

> predict performance.

>

> Doug

<= p class=3DMsoPlainText>>

> Dou= glas Burns

> Signal Integrity Soft= ware, Inc

> 6 Clock Tower Place

> Maynard, MA 01754

> 978-461-0449 x14

>

> 

> -----Original Message-----

> From: owner-ibis-users@eda.org

> [mailto:owner-ibis-users@eda.org] On Behalf Of Sc= ott McMorrow

> Sent: Wednesday, Ju= ne 01, 2011 9:33 AM

> To: bradb@si= grity.com

> Cc: 'Ray Anderson'; 'i= bis-users'

> Subject: Re: [IBIS-Us= ers] Requesting for some help /

>= information regarding the use of IBIS in SI simulation.

>

> Brad

>

> It is certainly your prerogative to disagree with me.  In t= he

> context of the original ques= tion, we are not talking about

> = randomly distributed RLC, but rather package connections from

> board to silicon, which is the case in most = IBIS models. 

> Given that, = we know the general topology. 

= > Whether the package uses lead frame, 2 layer FC packaging, =

> 2/4 layer organic wire bond packaging, or = multilayer buildup

> packaging, a= single path from die to ball looks remarkably

> similar to cascaded transmission lines.  Even bond wir= es look

> like transmission lines= .

>

> If I'm given a single RLC for an IBIS model of a <= /p>

> conventionally packaged silicon device , th= en I can guarantee

> you that the= simulation will be more faithful to measurements

> when the transmission line equivalent is used, rather = than

> lumped elements.  Bee= n there, done the measurements many,

> many times.  When multiple sections are specified in the IBIS

> .pkg format, then there is no amb= iguity, a non-zero RLC

> section = length defines a distributed element, and a zero

> length section defines a lumped element.  The simula= tor

> should model it as such.

>

> Having done correlation of package modeling to measurements =

> from DC to 40 GHz on a 12-layer buil= d-up with near zero

> error, I'm = well aware of the issues involved with using the

> wrong modeling method, and poor material modeling.  = I agree

> with you that a single = RLC is an extremely poor approximation

> of any complex package interconnect, or any interconnect for <= /o:p>

> that matter.  However, given tha= t a user is presented with an

> R= LC that was extracted with a quasi-static solver, as is the

=

> case with most IBIS models, I maintain that th= e result will

> be closer to real= ity when transformed into the distributed

> transmission line equivalent.  I've seen way too many cases=

> where simulators used a lumped= RLC directly, grossly over

> pre= dicting  ringing at the die and in the channel, and

> confirmed by physical measurements.

>

> W= hen we get into full-wave and hybrid full-wave AC modeling

<= p class=3DMsoPlainText>> of packages there are a host of other issues th= at we can

> discuss, such as accu= rate dielectric modeling, accurate

&= gt; surface roughness modeling, as-designed vs. as-built package

> geometries, +/- 15% impedance variation d= ue to manufacturing

> process&nbs= p; and electromagnetic non-locality.  But that is for

<= p class=3DMsoPlainText>> another time.

>

>

> best regards,

= >

> Scott

>

>

> 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

>

> TeraspeedR is= the registered service mark of Teraspeed

> Consulting Group LLC

> =

>

> On 6/1/2011 1:53 AM, Brad Brim wrote:

> > hello Scott,

> >

> > I don't agree w= ith you. Such simulators (or model extractors which

> > write

> = out

> > such "postprocesse= d" model data) are no more assured accurate than

> simply

> >= ; applying or writing out the base RLC data.

> >

> > Most pack= age extractors, especially ones you may refer to as

> > applicable "from the beginning", are ba= sed on static RLC

> simulation in=

> > which a

> single L

&g= t; > and C are extracted at exactly DC from two distinct simulations;

> > magnetostatic and electrosta= tic respectively. One has NO CLUE how to

> form

> > the equivalen= t circuit given only the static lumped L and C

> computed

> > i= ndependently. Of course, as asked and discussed by Ray, if

<= p class=3DMsoPlainText>> the user

> > has insight from the physical structure then a more broadband mo= del

> > MIGHT be generated, bu= t there is no guarantee!

> > On= e person assuming a PI circuit (with the C split equally

> in half -

= > > or

> even

=

> > unequally - and the L in the middle) and = another person

> assuming a TEE <= o:p>

> > circuit (with the L split a= nd the shunt C in the middle) are no more

> correct

> > than the = other. One has NO IDEA of the high frequency

> behavior of the

> &= gt; circuit (either just above the quasistatic limit where the likely<= /o:p>

> spectral

> > content is relevant or higher where it is less likely r= elevant)

> > without

> some

> > form of AC high-frequency simulation or measurement. The <= /o:p>

> behavior at

> > "infinite" frequency in meaningless and= to argue that a uniformly

> >= distributed multi-stage ladder network is valid has no more

=

> justification

> > than another person arguing it should me a lowpass network = with all

> > the inductance on= the die side because of wirebond inductance. This

> > argument

&g= t; has

> > blindly been accepte= d and argued for many years. It has been

> > unjustified

> and

> > wrong, as you would say, &qu= ot;from the beginning".

> >= ;

> > Want a valid model at hig= her frequencies, then extract AC

>= ; information

> from

> > which to generate it. One's guess or int= uitive argument without AC

> >= information to back it up is only a guess, as Andy stated. The =

> > classical uniformly distributed ladde= r network is a

> deceptively simp= le

> > and

> intuitively

&= gt; > pleasing assumption that is easy to understand and unfortunately

> accepted by

> > way too many people in the industry. This suppos= ed more

> accurate guess

> has

> > failed in too many cases and can even be worse than a

> simple totally

> > unbalanced low pass filter assumption over the fr= equency

> spectrum of =

> > relevance.

> >

> > Many = commercially available RLC extractors continue to make this

<= p class=3DMsoPlainText>> assumption

> > today. Users are placed at significant risk because they falsel= y

> > believe

> the

> &= gt; model is in some sense "broadband" or "wideband". I= t is a

> guess with

> > no guarantee to be any better than any = other assumed more

> distributed =

> > equivalent circuit for whi= ch there is no theoretical or physical

> > justification.

> >=

> > If one starts with AC data= , assumes an equivalent circuit and *then*

> selects

> > element = values in such to fit the data then there is reason to argue

=

> this is

= > > a more valid model at higher frequencies. One cannot do

> this from only

> DC

> > termin= al-based data. Not that it's difficult, it is impossible.

> >

> &= gt; best regards,

> > &nbs= p; -Brad

> >

> >

> &g= t;> -----Original Message-----

>= ; >> From: owner-ibis-users@eda.org

> >> [mailto:owner-ibis-users@eda.org] On Behalf Of Scott McM= orrow

> >> Sent: Tuesday, Ma= y 31, 2011 5:04 PM

> >> To: = Ray Anderson

> >> Cc: ibis-u= sers; Ray Anderson

> >> Subj= ect: Re: [IBIS-Users] Requesting for some help / information

> >> regarding the use of IBIS in SI simu= lation.

> >>

<= p class=3DMsoPlainText>> >> Since the beginning of IBIS, the most = accurate simulators

> would turn =

> >> the RLC package parasi= tics into a transmission line

> e= quivalent.  In

> >> li= eu of any additional information it is the most

> reasonable thing to

> >> do, since packages can be approximated as transmission lines= .

> >>

> >>

> &= gt;> Scott McMorrow

> >> = Teraspeed Consulting Group LLC

> &= gt;> 121 North River Drive

> &g= t;> Narragansett, RI 02882

> &g= t;> (401) 284-1827 Business

> &= gt;> (401) 284-1840 Fax

> >&= gt;

> >> http://www.teraspee= d.com

> >>

> >> TeraspeedR is the registered service mar= k of Teraspeed Consulting

> >&= gt; Group LLC

> >>

> >>

> >> On 5/31/2011 7:59 PM, Ray Anderson wrote:

> >>> If you are using extracted RLC d= ata to manually set up

> the pack= age

> >>> model you can = certainly make intelligent decisions on the

> >> topology of

>= >>> the model and the distribution of the RLC parasitics.

> >> However if you

<= p class=3DMsoPlainText>> >>> are depending on a simulator to re= ad the data from a IBIS

> >>= .pkg format

> >>> file (= or the [PIN] data) and set up a model for you then

> >> your results

> >>> may differ from simulator to simulator.<= /p>

> >>>

> >>> -Ray

> &= gt;>> Xilinx Inc.

> >>= >

> >>>

=

> >>> -----Original Message-----

> >>> From: owner-ibis-users@ed= a.org

> [mailto:owner-ibis-users@= eda.org] On

> >>> Behalf= Of Andrew Ingraham

> >>>= Sent: Tuesday, May 31, 2011 4:48 PM

= > >>> To: ibis-users

>= >>> Subject: Re: [IBIS-Users] Requesting for some help / informat= ion

> >>> regarding the = use of IBIS in SI simulation.

> &g= t;>>

> >>> Yes.

> >>>

> >>> I am usually tempted to start with an eve= nly distributed

> >> RLC mod= el ...

> >>> unless I hav= e reason to think that the distribution is

> >> otherwise.  For

> >>> example, wirebonds might have most of the inductance = and

> >> resistance,

> >>> whereas the leadframe may = have more capacitance, which

> >= ;> might influence

> >>&g= t; one to imbalance those factors unequally between die end

<= p class=3DMsoPlainText>> >> and pin end.

> >>> But without hard data to back it up, that is= just guessing.

> >>>

> >>> Andy

> >>>

> >> --

> >> This= message has been scanned for viruses and dangerous content by <= /p>

> >> MailScanner, and is believed to be= clean.

> >>

<= p class=3DMsoPlainText>> >>

> --------------------------------------------------------------------<= o:p>

> >> |For help or to subscri= be/unsubscribe, e-mail

> majordom= o@eda-stds.org

> >> |with t= he appropriate command message(s) in the body:

> >> |

> >&g= t; |  help

> >> | = subscribe   ibis<optional e-mail address, if different>

> >> |  subscribe &n= bsp; ibis-users<optional e-mail address, if different>

=

> >> |  unsubscribe ibis<optional = e-mail address, if different> 

> >> | unsubscribe ibis-users<optional e-mail address, if di= fferent>

> >> |

> >> |or e-mail a request to ibis-req= uest@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

> >>

>

> --

> This message has been scanned for viruses and dangerous <= /o:p>

> content by MailScanner, and is believ= ed to be clean.

>

<= p class=3DMsoPlainText>> -----------------------------------------------= - ---------------------

> |For help = or to subscribe/unsubscribe, e-mail majordomo@eda-stds.org

<= p class=3DMsoPlainText>> |with the appropriate command message(s) in the= body:

> |

> |  help

>= ; |  subscribe   ibis       &l= t;optional e-mail address, if different>

> |  subscribe   ibis-users <optional e-mail ad= dress, if different>

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> |  = unsubscribe ibis-users <optional e-mail address, if different>

> |

> |or e-mail a request to ibis-request@eda-stds.org.

> |

> |IBI= S 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

>

 


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


--=20
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean. - ------_=_NextPart_001_01CC212B.B13B969F-- - -------------------------------------------------------------------- |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: Wed, 8 Jun 2011 13:36:11 +0300 From: "Maher, Amin" Subject: [IBIS-Users] mutual inductance in EBD files - ------_=_NextPart_001_01CC25C7.E4659C69 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Hello experts, =20 Is there a way to describe mutual inductance (coupling) between EBD paths. =20 Regards, Amin Maher=20 - --=20 This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. - ------_=_NextPart_001_01CC25C7.E4659C69 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Hello experts,

 

Is there a way to describe mutual inductance (coupling) between EBD paths.=

 

Regards,

Amin Maher


--=20
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean. - ------_=_NextPart_001_01CC25C7.E4659C69-- - -------------------------------------------------------------------- |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: Thu, 2 Jun 2011 07:55:05 -0400 (EDT) From: "Walter Katz" Subject: RE: [IBIS-Users] Requesting for some help / information regarding the use of IBIS in SI simulation. All, IBIS is now discussing enhancements to the IBIS Package Models to support complex, broadband and coupled package models. There will be presentations made at the IBIS Summit next week at DAC on two proposals, both using a soon to be approved IBIS Interconnect Spice Subckt (IBIS-ISS) language. IBIS-ISS is a subset of HSPICE that the EDA Vendors in IBS have agreed to. This new package model interface should address all of the issues that have been raised in this e-mail thread. All interested parties should carefully review what is being proposed to insure that these issues are correctly addressed. Walter - -----Original Message----- From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf Of Brad Brim Sent: Thursday, June 02, 2011 5:55 AM To: 'Doug Burns'; 'Scott McMorrow' Cc: 'Ray Anderson'; 'ibis-users' Subject: RE: [IBIS-Users] Requesting for some help / information regarding the use of IBIS in SI simulation. hi guys, Guess we'll agree to disagree. I have experience with any number of simple packages that violate your "better" supposition for a uniformly distributed TL model. Why would this occur, because I completely agree with you that it is counter intuitive. From a package I recently characterized in some detail for system SI/PI analysis; let's say the net behaves as static RLC to 2Ghz, then at about 4GHz there is some form of resonance in the signals or the planes. There's a suckout in the response and then at higher frequencies it behaves more like the TL you guys propose. If you assume the TL, then you completely miss this behavior, and I do mean "completely". For this DDR bus you probably don't care about the spectrum above 8GHz where it is again more TL like. But you certainly DO care about the spectrum between 2Ghz and 6Ghz where it looks nothing like a TL. If I choose properly a TEE or PI circuit to model the behavior in this mid frequency range (since either works to 2Ghz) then you get a much better transient system-level simulation than using your proposed TL model. This is true even though the TEE/PI response at higher frequencies is much worse than the uniform TL model. There is energy in the mid spectrum but not in the high spectrum for this application. If I use a multi-stage RLC model then select the element values to fit the broadband response then I can get match at both mid and high frequencies to well 10Ghz and make all of us happier (but maybe not to 40GHz). This is NOT a corner case. I see it in many of the package I characterize. If I was trying to do a best fit to 40Ghz for this same package because my signals had energy spread out that broadband, then it would probably be better to use the uniform TL model. However, not all applications call for it and the system is much better characterized with a model more correct where the signals actually have energy. cheers, -Brad > -----Original Message----- > From: Doug Burns [mailto:dburns@sisoft.com] > Sent: Wednesday, June 01, 2011 6:55 AM > To: 'Scott McMorrow'; bradb@sigrity.com > Cc: 'Ray Anderson'; 'ibis-users' > Subject: RE: [IBIS-Users] Requesting for some help / information > regarding the use of IBIS in SI simulation. > > All, > > I have to agree with Scott on this. For the type of packages as > outlined by Scott, if one were to take the detailed model from a > simulator and decompose it to a RLC format, the best correlation > between the detailed model and the simplified model will occur when > the simplified RLC is treated as a distributed structure such as a > transmission line. Like Scott, we have proven this multiple time on a > wide variety of package styles (leadframe through 24+ layer packages). > There is no disagreement that a detailed model will be better, > especially for high frequencies, but we must work within the limits of > what IBIS can support. The mode detailed that package description is > in IBIS, the better estimation we can make, but using lumped data for > high speed signals is just causing an issue where one really will not > exist. EDA tools need to make the best estimation of the available > data to predict performance. > > Doug > > Douglas Burns > Signal Integrity Software, Inc > 6 Clock Tower Place > Maynard, MA 01754 > 978-461-0449 x14 > > > -----Original Message----- > From: owner-ibis-users@eda.org > [mailto:owner-ibis-users@eda.org] On Behalf Of Scott McMorrow > Sent: Wednesday, June 01, 2011 9:33 AM > To: bradb@sigrity.com > Cc: 'Ray Anderson'; 'ibis-users' > Subject: Re: [IBIS-Users] Requesting for some help / information > regarding the use of IBIS in SI simulation. > > Brad > > It is certainly your prerogative to disagree with me. In the context > of the original question, we are not talking about randomly > distributed RLC, but rather package connections from board to silicon, > which is the case in most IBIS models. > Given that, we know the general topology. > Whether the package uses lead frame, 2 layer FC packaging, > 2/4 layer organic wire bond packaging, or multilayer buildup > packaging, a single path from die to ball looks remarkably similar to > cascaded transmission lines. Even bond wires look like transmission > lines. > > If I'm given a single RLC for an IBIS model of a conventionally > packaged silicon device , then I can guarantee you that the simulation > will be more faithful to measurements when the transmission line > equivalent is used, rather than lumped elements. Been there, done the > measurements many, many times. When multiple sections are specified > in the IBIS .pkg format, then there is no ambiguity, a non-zero RLC > section length defines a distributed element, and a zero length > section defines a lumped element. The simulator should model it as > such. > > Having done correlation of package modeling to measurements from DC to > 40 GHz on a 12-layer build-up with near zero error, I'm well aware of > the issues involved with using the wrong modeling method, and poor > material modeling. I agree with you that a single RLC is an extremely > poor approximation of any complex package interconnect, or any > interconnect for that matter. However, given that a user is presented > with an RLC that was extracted with a quasi-static solver, as is the > case with most IBIS models, I maintain that the result will be closer > to reality when transformed into the distributed transmission line > equivalent. I've seen way too many cases where simulators used a > lumped RLC directly, grossly over predicting ringing at the die and > in the channel, and confirmed by physical measurements. > > When we get into full-wave and hybrid full-wave AC modeling of > packages there are a host of other issues that we can discuss, such as > accurate dielectric modeling, accurate surface roughness modeling, > as-designed vs. as-built package geometries, +/- 15% impedance > variation due to manufacturing process and electromagnetic > non-locality. But that is for another time. > > > best regards, > > Scott > > > 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 > > TeraspeedR is the registered service mark of Teraspeed > Consulting Group LLC > > > On 6/1/2011 1:53 AM, Brad Brim wrote: > > hello Scott, > > > > I don't agree with you. Such simulators (or model extractors which > > write > out > > such "postprocessed" model data) are no more assured accurate than > simply > > applying or writing out the base RLC data. > > > > Most package extractors, especially ones you may refer to as > > applicable "from the beginning", are based on static RLC > simulation in > > which a > single L > > and C are extracted at exactly DC from two distinct simulations; > > magnetostatic and electrostatic respectively. One has NO CLUE how to > form > > the equivalent circuit given only the static lumped L and C > computed > > independently. Of course, as asked and discussed by Ray, if > the user > > has insight from the physical structure then a more broadband model > > MIGHT be generated, but there is no guarantee! > > One person assuming a PI circuit (with the C split equally > in half - > > or > even > > unequally - and the L in the middle) and another person > assuming a TEE > > circuit (with the L split and the shunt C in the middle) are no more > correct > > than the other. One has NO IDEA of the high frequency > behavior of the > > circuit (either just above the quasistatic limit where the likely > spectral > > content is relevant or higher where it is less likely relevant) > > without > some > > form of AC high-frequency simulation or measurement. The > behavior at > > "infinite" frequency in meaningless and to argue that a uniformly > > distributed multi-stage ladder network is valid has no more > justification > > than another person arguing it should me a lowpass network with all > > the inductance on the die side because of wirebond inductance. This > > argument > has > > blindly been accepted and argued for many years. It has been > > unjustified > and > > wrong, as you would say, "from the beginning". > > > > Want a valid model at higher frequencies, then extract AC > information > from > > which to generate it. One's guess or intuitive argument without AC > > information to back it up is only a guess, as Andy stated. The > > classical uniformly distributed ladder network is a > deceptively simple > > and > intuitively > > pleasing assumption that is easy to understand and unfortunately > accepted by > > way too many people in the industry. This supposed more > accurate guess > has > > failed in too many cases and can even be worse than a > simple totally > > unbalanced low pass filter assumption over the frequency > spectrum of > > relevance. > > > > Many commercially available RLC extractors continue to make this > assumption > > today. Users are placed at significant risk because they falsely > > believe > the > > model is in some sense "broadband" or "wideband". It is a > guess with > > no guarantee to be any better than any other assumed more > distributed > > equivalent circuit for which there is no theoretical or physical > > justification. > > > > If one starts with AC data, assumes an equivalent circuit and *then* > selects > > element values in such to fit the data then there is reason to argue > this is > > a more valid model at higher frequencies. One cannot do > this from only > DC > > terminal-based data. Not that it's difficult, it is impossible. > > > > best regards, > > -Brad > > > > > >> -----Original Message----- > >> From: owner-ibis-users@eda.org > >> [mailto:owner-ibis-users@eda.org] On Behalf Of Scott McMorrow > >> Sent: Tuesday, May 31, 2011 5:04 PM > >> To: Ray Anderson > >> Cc: ibis-users; Ray Anderson > >> Subject: Re: [IBIS-Users] Requesting for some help / information > >> regarding the use of IBIS in SI simulation. > >> > >> Since the beginning of IBIS, the most accurate simulators > would turn > >> the RLC package parasitics into a transmission line > equivalent. In > >> lieu of any additional information it is the most > reasonable thing to > >> do, since packages can be approximated as transmission lines. > >> > >> > >> 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 > >> > >> TeraspeedR is the registered service mark of Teraspeed Consulting > >> Group LLC > >> > >> > >> On 5/31/2011 7:59 PM, Ray Anderson wrote: > >>> If you are using extracted RLC data to manually set up > the package > >>> model you can certainly make intelligent decisions on the > >> topology of > >>> the model and the distribution of the RLC parasitics. > >> However if you > >>> are depending on a simulator to read the data from a IBIS > >> .pkg format > >>> file (or the [PIN] data) and set up a model for you then > >> your results > >>> may differ from simulator to simulator. > >>> > >>> -Ray > >>> Xilinx Inc. > >>> > >>> > >>> -----Original Message----- > >>> From: owner-ibis-users@eda.org > [mailto:owner-ibis-users@eda.org] On > >>> Behalf Of Andrew Ingraham > >>> Sent: Tuesday, May 31, 2011 4:48 PM > >>> To: ibis-users > >>> Subject: Re: [IBIS-Users] Requesting for some help / information > >>> regarding the use of IBIS in SI simulation. > >>> > >>> Yes. > >>> > >>> I am usually tempted to start with an evenly distributed > >> RLC model ... > >>> unless I have reason to think that the distribution is > >> otherwise. For > >>> example, wirebonds might have most of the inductance and > >> resistance, > >>> whereas the leadframe may have more capacitance, which > >> might influence > >>> one to imbalance those factors unequally between die end > >> and pin end. > >>> But without hard data to back it up, that is just guessing. > >>> > >>> Andy > >>> > >> -- > >> This message has been scanned for viruses and dangerous content by > >> MailScanner, and is believed to be clean. > >> > >> > -------------------------------------------------------------------- > >> |For help or to subscribe/unsubscribe, e-mail > 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 > >> > > -- > This message has been scanned for viruses and dangerous > content by MailScanner, and is believed to be clean. > > -------------------------------------------------------------------- > |For help or to subscribe/unsubscribe, e-mail 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 > - -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. - -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail 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 - -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. - -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail 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: Thu, 9 Jun 2011 10:03:55 -0700 From: "Muranyi, Arpad" Subject: RE: [IBIS-Users] mutual inductance in EBD files This is a multi-part message in MIME format. - ------_=_NextPart_001_01CC26C7.377DA9CE Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Amin, =20 Looks like the answer is NO. Even though the EBD syntax is almost identical to the package syntax for the multi-segment uncoupled T-line style trace descriptions, the lumped RLC coupled matrix syntax of package models is not available for EBD models. =20 Thanks, =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=3D=3D=3D =20 =20 From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf Of Maher, Amin Sent: Wednesday, June 08, 2011 5:36 AM To: ibis-users@eda.org Subject: [IBIS-Users] mutual inductance in EBD files =20 Hello experts, =20 Is there a way to describe mutual inductance (coupling) between EBD paths. =20 Regards, Amin Maher=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_01CC26C7.377DA9CE Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Amin,

 

Looks = like the answer is NO.  Even though the EBD syntax is

almost identical to the package syntax for the multi-= segment

uncoupled T-line style trace = descriptions, the lumped RLC

coupled = matrix syntax of package models is not available

for EBD models.

&nbs= p;

Thanks,

 

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=3D=3D=3D

 

&= nbsp;

From: owner-ibis-use= rs@eda.org [mailto:owner-ibis-users@eda.org] On Behalf Of Maher, Ami= n
Sent: Wednesday, June 08, 2011 5:36 AM
To: ibis-users= @eda.org
Subject: [IBIS-Users] mutual inductance in EBD files

 

Hello experts,

&n= bsp;

Is there a way to describe mutual induct= ance (coupling) between EBD paths.

=  

Regards,

Amin Maher


--
This message ha= s been scanned for viruses and
dangerous content by MailScanner, and is
believed to be cle= an.


--=20
This message has been scanned for viruses and
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believed to be clean. - ------_=_NextPart_001_01CC26C7.377DA9CE-- - -------------------------------------------------------------------- |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: Thu, 2 Jun 2011 02:55:03 -0700 From: "Brad Brim" Subject: RE: [IBIS-Users] Requesting for some help / information regarding the use of IBIS in SI simulation. hi guys, Guess we'll agree to disagree. I have experience with any number of simple packages that violate your "better" supposition for a uniformly distributed TL model. Why would this occur, because I completely agree with you that it is counter intuitive. From a package I recently characterized in some detail for system SI/PI analysis; let's say the net behaves as static RLC to 2Ghz, then at about 4GHz there is some form of resonance in the signals or the planes. There's a suckout in the response and then at higher frequencies it behaves more like the TL you guys propose. If you assume the TL, then you completely miss this behavior, and I do mean "completely". For this DDR bus you probably don't care about the spectrum above 8GHz where it is again more TL like. But you certainly DO care about the spectrum between 2Ghz and 6Ghz where it looks nothing like a TL. If I choose properly a TEE or PI circuit to model the behavior in this mid frequency range (since either works to 2Ghz) then you get a much better transient system-level simulation than using your proposed TL model. This is true even though the TEE/PI response at higher frequencies is much worse than the uniform TL model. There is energy in the mid spectrum but not in the high spectrum for this application. If I use a multi-stage RLC model then select the element values to fit the broadband response then I can get match at both mid and high frequencies to well 10Ghz and make all of us happier (but maybe not to 40GHz). This is NOT a corner case. I see it in many of the package I characterize. If I was trying to do a best fit to 40Ghz for this same package because my signals had energy spread out that broadband, then it would probably be better to use the uniform TL model. However, not all applications call for it and the system is much better characterized with a model more correct where the signals actually have energy. cheers, -Brad > -----Original Message----- > From: Doug Burns [mailto:dburns@sisoft.com] > Sent: Wednesday, June 01, 2011 6:55 AM > To: 'Scott McMorrow'; bradb@sigrity.com > Cc: 'Ray Anderson'; 'ibis-users' > Subject: RE: [IBIS-Users] Requesting for some help / > information regarding the use of IBIS in SI simulation. > > All, > > I have to agree with Scott on this. For the type of packages > as outlined by Scott, if one were to take the detailed model > from a simulator and decompose it to a RLC format, the best > correlation between the detailed model and the simplified > model will occur when the simplified RLC is treated as a > distributed structure such as a transmission line. Like > Scott, we have proven this multiple time on a wide variety of > package styles (leadframe through 24+ layer packages). There > is no disagreement that a detailed model will be better, > especially for high frequencies, but we must work within the > limits of what IBIS can support. The mode detailed that > package description is in IBIS, the better estimation we can > make, but using lumped data for high speed signals is just > causing an issue where one really will not exist. EDA tools > need to make the best estimation of the available data to > predict performance. > > Doug > > Douglas Burns > Signal Integrity Software, Inc > 6 Clock Tower Place > Maynard, MA 01754 > 978-461-0449 x14 > > > -----Original Message----- > From: owner-ibis-users@eda.org > [mailto:owner-ibis-users@eda.org] On Behalf Of Scott McMorrow > Sent: Wednesday, June 01, 2011 9:33 AM > To: bradb@sigrity.com > Cc: 'Ray Anderson'; 'ibis-users' > Subject: Re: [IBIS-Users] Requesting for some help / > information regarding the use of IBIS in SI simulation. > > Brad > > It is certainly your prerogative to disagree with me. In the > context of the original question, we are not talking about > randomly distributed RLC, but rather package connections from > board to silicon, which is the case in most IBIS models. > Given that, we know the general topology. > Whether the package uses lead frame, 2 layer FC packaging, > 2/4 layer organic wire bond packaging, or multilayer buildup > packaging, a single path from die to ball looks remarkably > similar to cascaded transmission lines. Even bond wires look > like transmission lines. > > If I'm given a single RLC for an IBIS model of a > conventionally packaged silicon device , then I can guarantee > you that the simulation will be more faithful to measurements > when the transmission line equivalent is used, rather than > lumped elements. Been there, done the measurements many, > many times. When multiple sections are specified in the IBIS > .pkg format, then there is no ambiguity, a non-zero RLC > section length defines a distributed element, and a zero > length section defines a lumped element. The simulator > should model it as such. > > Having done correlation of package modeling to measurements > from DC to 40 GHz on a 12-layer build-up with near zero > error, I'm well aware of the issues involved with using the > wrong modeling method, and poor material modeling. I agree > with you that a single RLC is an extremely poor approximation > of any complex package interconnect, or any interconnect for > that matter. However, given that a user is presented with an > RLC that was extracted with a quasi-static solver, as is the > case with most IBIS models, I maintain that the result will > be closer to reality when transformed into the distributed > transmission line equivalent. I've seen way too many cases > where simulators used a lumped RLC directly, grossly over > predicting ringing at the die and in the channel, and > confirmed by physical measurements. > > When we get into full-wave and hybrid full-wave AC modeling > of packages there are a host of other issues that we can > discuss, such as accurate dielectric modeling, accurate > surface roughness modeling, as-designed vs. as-built package > geometries, +/- 15% impedance variation due to manufacturing > process and electromagnetic non-locality. But that is for > another time. > > > best regards, > > Scott > > > 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 > > TeraspeedR is the registered service mark of Teraspeed > Consulting Group LLC > > > On 6/1/2011 1:53 AM, Brad Brim wrote: > > hello Scott, > > > > I don't agree with you. Such simulators (or model extractors which > > write > out > > such "postprocessed" model data) are no more assured accurate than > simply > > applying or writing out the base RLC data. > > > > Most package extractors, especially ones you may refer to as > > applicable "from the beginning", are based on static RLC > simulation in > > which a > single L > > and C are extracted at exactly DC from two distinct simulations; > > magnetostatic and electrostatic respectively. One has NO CLUE how to > form > > the equivalent circuit given only the static lumped L and C > computed > > independently. Of course, as asked and discussed by Ray, if > the user > > has insight from the physical structure then a more broadband model > > MIGHT be generated, but there is no guarantee! > > One person assuming a PI circuit (with the C split equally > in half - > > or > even > > unequally - and the L in the middle) and another person > assuming a TEE > > circuit (with the L split and the shunt C in the middle) are no more > correct > > than the other. One has NO IDEA of the high frequency > behavior of the > > circuit (either just above the quasistatic limit where the likely > spectral > > content is relevant or higher where it is less likely relevant) > > without > some > > form of AC high-frequency simulation or measurement. The > behavior at > > "infinite" frequency in meaningless and to argue that a uniformly > > distributed multi-stage ladder network is valid has no more > justification > > than another person arguing it should me a lowpass network with all > > the inductance on the die side because of wirebond inductance. This > > argument > has > > blindly been accepted and argued for many years. It has been > > unjustified > and > > wrong, as you would say, "from the beginning". > > > > Want a valid model at higher frequencies, then extract AC > information > from > > which to generate it. One's guess or intuitive argument without AC > > information to back it up is only a guess, as Andy stated. The > > classical uniformly distributed ladder network is a > deceptively simple > > and > intuitively > > pleasing assumption that is easy to understand and unfortunately > accepted by > > way too many people in the industry. This supposed more > accurate guess > has > > failed in too many cases and can even be worse than a > simple totally > > unbalanced low pass filter assumption over the frequency > spectrum of > > relevance. > > > > Many commercially available RLC extractors continue to make this > assumption > > today. Users are placed at significant risk because they falsely > > believe > the > > model is in some sense "broadband" or "wideband". It is a > guess with > > no guarantee to be any better than any other assumed more > distributed > > equivalent circuit for which there is no theoretical or physical > > justification. > > > > If one starts with AC data, assumes an equivalent circuit and *then* > selects > > element values in such to fit the data then there is reason to argue > this is > > a more valid model at higher frequencies. One cannot do > this from only > DC > > terminal-based data. Not that it's difficult, it is impossible. > > > > best regards, > > -Brad > > > > > >> -----Original Message----- > >> From: owner-ibis-users@eda.org > >> [mailto:owner-ibis-users@eda.org] On Behalf Of Scott McMorrow > >> Sent: Tuesday, May 31, 2011 5:04 PM > >> To: Ray Anderson > >> Cc: ibis-users; Ray Anderson > >> Subject: Re: [IBIS-Users] Requesting for some help / information > >> regarding the use of IBIS in SI simulation. > >> > >> Since the beginning of IBIS, the most accurate simulators > would turn > >> the RLC package parasitics into a transmission line > equivalent. In > >> lieu of any additional information it is the most > reasonable thing to > >> do, since packages can be approximated as transmission lines. > >> > >> > >> 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 > >> > >> TeraspeedR is the registered service mark of Teraspeed Consulting > >> Group LLC > >> > >> > >> On 5/31/2011 7:59 PM, Ray Anderson wrote: > >>> If you are using extracted RLC data to manually set up > the package > >>> model you can certainly make intelligent decisions on the > >> topology of > >>> the model and the distribution of the RLC parasitics. > >> However if you > >>> are depending on a simulator to read the data from a IBIS > >> .pkg format > >>> file (or the [PIN] data) and set up a model for you then > >> your results > >>> may differ from simulator to simulator. > >>> > >>> -Ray > >>> Xilinx Inc. > >>> > >>> > >>> -----Original Message----- > >>> From: owner-ibis-users@eda.org > [mailto:owner-ibis-users@eda.org] On > >>> Behalf Of Andrew Ingraham > >>> Sent: Tuesday, May 31, 2011 4:48 PM > >>> To: ibis-users > >>> Subject: Re: [IBIS-Users] Requesting for some help / information > >>> regarding the use of IBIS in SI simulation. > >>> > >>> Yes. > >>> > >>> I am usually tempted to start with an evenly distributed > >> RLC model ... > >>> unless I have reason to think that the distribution is > >> otherwise. For > >>> example, wirebonds might have most of the inductance and > >> resistance, > >>> whereas the leadframe may have more capacitance, which > >> might influence > >>> one to imbalance those factors unequally between die end > >> and pin end. > >>> But without hard data to back it up, that is just guessing. > >>> > >>> Andy > >>> > >> -- > >> This message has been scanned for viruses and dangerous content by > >> MailScanner, and is believed to be clean. > >> > >> > -------------------------------------------------------------------- > >> |For help or to subscribe/unsubscribe, e-mail > 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 > >> > > -- > This message has been scanned for viruses and dangerous > content by MailScanner, and is believed to be clean. > > -------------------------------------------------------------------- > |For help or to subscribe/unsubscribe, e-mail 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 > - -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. - -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail 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: Wed, 1 Jun 2011 09:55:03 -0400 (EDT) From: "Doug Burns" Subject: RE: [IBIS-Users] Requesting for some help / information regarding the use of IBIS in SI simulation. All, I have to agree with Scott on this. For the type of packages as outlined by Scott, if one were to take the detailed model from a simulator and decompose it to a RLC format, the best correlation between the detailed model and the simplified model will occur when the simplified RLC is treated as a distributed structure such as a transmission line. Like Scott, we have proven this multiple time on a wide variety of package styles (leadframe through 24+ layer packages). There is no disagreement that a detailed model will be better, especially for high frequencies, but we must work within the limits of what IBIS can support. The mode detailed that package description is in IBIS, the better estimation we can make, but using lumped data for high speed signals is just causing an issue where one really will not exist. EDA tools need to make the best estimation of the available data to predict performance. Doug Douglas Burns Signal Integrity Software, Inc 6 Clock Tower Place Maynard, MA 01754 978-461-0449 x14 - -----Original Message----- From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf Of Scott McMorrow Sent: Wednesday, June 01, 2011 9:33 AM To: bradb@sigrity.com Cc: 'Ray Anderson'; 'ibis-users' Subject: Re: [IBIS-Users] Requesting for some help / information regarding the use of IBIS in SI simulation. Brad It is certainly your prerogative to disagree with me. In the context of the original question, we are not talking about randomly distributed RLC, but rather package connections from board to silicon, which is the case in most IBIS models. Given that, we know the general topology. Whether the package uses lead frame, 2 layer FC packaging, 2/4 layer organic wire bond packaging, or multilayer buildup packaging, a single path from die to ball looks remarkably similar to cascaded transmission lines. Even bond wires look like transmission lines. If I'm given a single RLC for an IBIS model of a conventionally packaged silicon device , then I can guarantee you that the simulation will be more faithful to measurements when the transmission line equivalent is used, rather than lumped elements. Been there, done the measurements many, many times. When multiple sections are specified in the IBIS .pkg format, then there is no ambiguity, a non-zero RLC section length defines a distributed element, and a zero length section defines a lumped element. The simulator should model it as such. Having done correlation of package modeling to measurements from DC to 40 GHz on a 12-layer build-up with near zero error, I'm well aware of the issues involved with using the wrong modeling method, and poor material modeling. I agree with you that a single RLC is an extremely poor approximation of any complex package interconnect, or any interconnect for that matter. However, given that a user is presented with an RLC that was extracted with a quasi-static solver, as is the case with most IBIS models, I maintain that the result will be closer to reality when transformed into the distributed transmission line equivalent. I've seen way too many cases where simulators used a lumped RLC directly, grossly over predicting ringing at the die and in the channel, and confirmed by physical measurements. When we get into full-wave and hybrid full-wave AC modeling of packages there are a host of other issues that we can discuss, such as accurate dielectric modeling, accurate surface roughness modeling, as-designed vs. as-built package geometries, +/- 15% impedance variation due to manufacturing process and electromagnetic non-locality. But that is for another time. best regards, Scott 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 TeraspeedR is the registered service mark of Teraspeed Consulting Group LLC On 6/1/2011 1:53 AM, Brad Brim wrote: > hello Scott, > > I don't agree with you. Such simulators (or model extractors which write out > such "postprocessed" model data) are no more assured accurate than simply > applying or writing out the base RLC data. > > Most package extractors, especially ones you may refer to as applicable > "from the beginning", are based on static RLC simulation in which a single L > and C are extracted at exactly DC from two distinct simulations; > magnetostatic and electrostatic respectively. One has NO CLUE how to form > the equivalent circuit given only the static lumped L and C computed > independently. Of course, as asked and discussed by Ray, if the user has > insight from the physical structure then a more broadband model MIGHT be > generated, but there is no guarantee! > One person assuming a PI circuit (with the C split equally in half - or even > unequally - and the L in the middle) and another person assuming a TEE > circuit (with the L split and the shunt C in the middle) are no more correct > than the other. One has NO IDEA of the high frequency behavior of the > circuit (either just above the quasistatic limit where the likely spectral > content is relevant or higher where it is less likely relevant) without some > form of AC high-frequency simulation or measurement. The behavior at > "infinite" frequency in meaningless and to argue that a uniformly > distributed multi-stage ladder network is valid has no more justification > than another person arguing it should me a lowpass network with all the > inductance on the die side because of wirebond inductance. This argument has > blindly been accepted and argued for many years. It has been unjustified and > wrong, as you would say, "from the beginning". > > Want a valid model at higher frequencies, then extract AC information from > which to generate it. One's guess or intuitive argument without AC > information to back it up is only a guess, as Andy stated. The classical > uniformly distributed ladder network is a deceptively simple and intuitively > pleasing assumption that is easy to understand and unfortunately accepted by > way too many people in the industry. This supposed more accurate guess has > failed in too many cases and can even be worse than a simple totally > unbalanced low pass filter assumption over the frequency spectrum of > relevance. > > Many commercially available RLC extractors continue to make this assumption > today. Users are placed at significant risk because they falsely believe the > model is in some sense "broadband" or "wideband". It is a guess with no > guarantee to be any better than any other assumed more distributed > equivalent circuit for which there is no theoretical or physical > justification. > > If one starts with AC data, assumes an equivalent circuit and *then* selects > element values in such to fit the data then there is reason to argue this is > a more valid model at higher frequencies. One cannot do this from only DC > terminal-based data. Not that it's difficult, it is impossible. > > best regards, > -Brad > > >> -----Original Message----- >> From: owner-ibis-users@eda.org >> [mailto:owner-ibis-users@eda.org] On Behalf Of Scott McMorrow >> Sent: Tuesday, May 31, 2011 5:04 PM >> To: Ray Anderson >> Cc: ibis-users; Ray Anderson >> Subject: Re: [IBIS-Users] Requesting for some help / >> information regarding the use of IBIS in SI simulation. >> >> Since the beginning of IBIS, the most accurate simulators >> would turn the RLC package parasitics into a transmission >> line equivalent. In lieu of any additional information it is >> the most reasonable thing to do, since packages can be >> approximated as transmission lines. >> >> >> 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 >> >> TeraspeedR is the registered service mark of Teraspeed >> Consulting Group LLC >> >> >> On 5/31/2011 7:59 PM, Ray Anderson wrote: >>> If you are using extracted RLC data to manually set up the package >>> model you can certainly make intelligent decisions on the >> topology of >>> the model and the distribution of the RLC parasitics. >> However if you >>> are depending on a simulator to read the data from a IBIS >> .pkg format >>> file (or the [PIN] data) and set up a model for you then >> your results >>> may differ from simulator to simulator. >>> >>> -Ray >>> Xilinx Inc. >>> >>> >>> -----Original Message----- >>> From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On >>> Behalf Of Andrew Ingraham >>> Sent: Tuesday, May 31, 2011 4:48 PM >>> To: ibis-users >>> Subject: Re: [IBIS-Users] Requesting for some help / information >>> regarding the use of IBIS in SI simulation. >>> >>> Yes. >>> >>> I am usually tempted to start with an evenly distributed >> RLC model ... >>> unless I have reason to think that the distribution is >> otherwise. For >>> example, wirebonds might have most of the inductance and >> resistance, >>> whereas the leadframe may have more capacitance, which >> might influence >>> one to imbalance those factors unequally between die end >> and pin end. >>> But without hard data to back it up, that is just guessing. >>> >>> Andy >>> >> -- >> This message has been scanned for viruses and dangerous >> content by MailScanner, and is believed to be clean. >> >> -------------------------------------------------------------------- >> |For help or to subscribe/unsubscribe, e-mail 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 >> - -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. - -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail 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 - -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. - -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail 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: Tue, 31 May 2011 23:42:33 -0700 From: "Brad Brim" Subject: RE: [IBIS-Users] IBIS ver5.0 [composite current] and [ISSO PU/PD] This is a multi-part message in MIME format. - ------=_NextPart_000_0138_01CC1FEC.6AB8A350 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit hello Yuancheng, there will be a talk at the upcoming DAC IBIS forum that may be of interest to you. In summary, the BIRD-95/98 power-aware IBIS features work surprisingly well to match the balance of pwr/gnd/signal currents you observe in transistor-level models. To apply power-aware IBIS models you will need both a transistor-to-behavioral model translator as well as a circuit simulator than can each apply IBIS 5.0 compliant models. Both are available commercially, though not yet common. cheers, -Brad For reference you might want to see http://www.eda.org/ibis/summits/may11/wolff.pdf Also, coming up will be IBIS SUMMIT MEETING, DAC, San Diego, CA, USA Tuesday, June 7, 2011 9:00 AM IBIS PDN Feature Simulation Studies Randy Wolff, Micron Lance Wang, IO Methodology _____ From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf Of ji xiao Sent: Tuesday, May 31, 2011 11:20 PM To: ibis-users Subject: [IBIS-Users] IBIS ver5.0 [composite current] and [ISSO PU/PD] Dear all, As I know, for solving the SSN problem, IBIS version 5.0 adds section [composite current] and [ISSO PU/PD]. Then I have some questions: 1. How will the simulator work with the [composite current]? Does it directly adopt the power terminal current value at the [composite current] when the input voltage over the threshold voltage? But I feel different rise/fall time will lead to different current value at the power terminal. 2. The section [ISSO PU/PD] is likely to provide a gate modulation coefficent on the original output current. In specification, the Ipu=Kpu(t)*Ipu(Vcc-Vout(t))*Ksso_pu(Vtable_pu) and Ipd=Kpd(t)*Ipd(Vout(t))*Ksso_pd(Vtabke_pd). so does it mean the total output current is Ipu+Ipd? how does the simulator decide the value of Kpu(t) and Kpd(t) according to the data in IBIS file? Thanks and regards, Yuancheng - -- 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_0138_01CC1FEC.6AB8A350 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable
hello=20 Yuancheng,
 
there=20 will be a talk at the upcoming DAC IBIS forum that may be of interest to=20 you.
In=20 summary, the BIRD-95/98 power-aware IBIS features work surprisingly well to= =20 match the balance of pwr/gnd/signal currents you observe in transistor-leve= l=20 models.
To=20 apply power-aware IBIS models you will need both a transistor-to-behavioral= =20 model translator as well as a circuit simulator than can each apply IBIS 5.= 0=20 compliant models. Both are available commercially, though not yet=20 common.
 
cheers,
 -Brad
 
 
For=20 reference you might want to see http://www.eda.org= /ibis/summits/may11/wolff.pdf
 
Also,=20 coming up will be
IBIS SUMMIT MEETING, DAC, San Diego, CA, USA
Tuesday, June 7,= =20 2011
9:00 AM IBIS PDN Feature Simulation Studies
Randy Wolff,=20 Micron
Lance Wang, IO Methodology
 
 
From: owner-ibis-users@eda.org=20 [mailto:owner-ibis-users@eda.org] On Behalf Of ji xiao
Sent:= =20 Tuesday, May 31, 2011 11:20 PM
To: ibis-users
Subject:=20 [IBIS-Users] IBIS ver5.0 [composite current] and [ISSO=20 PU/PD]

Dear all,
As I know, for solving the SSN problem, IBIS version 5.0 adds sectio= n=20 [composite current] and [ISSO PU/PD]. Then I have some questions:
1. How will the simulator work with the [composite current]? Does it= =20 directly adopt the power terminal current value at the [composite current= ]=20 when the input voltage over the threshold voltage? But I feel different= =20 rise/fall time will lead to different current value at the power=20 terminal.
 
2. The section [ISSO PU/PD] is likely to provide a gate modulation= =20 coefficent on the original output current. In specification, the=20 Ipu=3DKpu(t)*Ipu(Vcc-Vout(t))*Ksso_pu(Vtable_pu) and=20 Ipd=3DKpd(t)*Ipd(Vout(t))*Ksso_pd(Vtabke_pd). so does it mean the total o= utput=20 current is Ipu+Ipd? how does the simulator decide the value of Kpu(t) and= =20 Kpd(t) according to the data in IBIS file?
 
Thanks and regards,
 
Yuancheng

--
This message has been scanned for viruses = and=20
dangerous content by MailScanner, and is=20
believed to be clean.
--=20
This message has been scanned for viruses and
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believed to be clean. - ------=_NextPart_000_0138_01CC1FEC.6AB8A350-- - -------------------------------------------------------------------- |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: Tue, 31 May 2011 22:53:17 -0700 From: "Brad Brim" Subject: RE: [IBIS-Users] Requesting for some help / information regarding the use of IBIS in SI simulation. hello Scott, I don't agree with you. Such simulators (or model extractors which write out such "postprocessed" model data) are no more assured accurate than simply applying or writing out the base RLC data. Most package extractors, especially ones you may refer to as applicable "from the beginning", are based on static RLC simulation in which a single L and C are extracted at exactly DC from two distinct simulations; magnetostatic and electrostatic respectively. One has NO CLUE how to form the equivalent circuit given only the static lumped L and C computed independently. Of course, as asked and discussed by Ray, if the user has insight from the physical structure then a more broadband model MIGHT be generated, but there is no guarantee! One person assuming a PI circuit (with the C split equally in half - or even unequally - and the L in the middle) and another person assuming a TEE circuit (with the L split and the shunt C in the middle) are no more correct than the other. One has NO IDEA of the high frequency behavior of the circuit (either just above the quasistatic limit where the likely spectral content is relevant or higher where it is less likely relevant) without some form of AC high-frequency simulation or measurement. The behavior at "infinite" frequency in meaningless and to argue that a uniformly distributed multi-stage ladder network is valid has no more justification than another person arguing it should me a lowpass network with all the inductance on the die side because of wirebond inductance. This argument has blindly been accepted and argued for many years. It has been unjustified and wrong, as you would say, "from the beginning". Want a valid model at higher frequencies, then extract AC information from which to generate it. One's guess or intuitive argument without AC information to back it up is only a guess, as Andy stated. The classical uniformly distributed ladder network is a deceptively simple and intuitively pleasing assumption that is easy to understand and unfortunately accepted by way too many people in the industry. This supposed more accurate guess has failed in too many cases and can even be worse than a simple totally unbalanced low pass filter assumption over the frequency spectrum of relevance. Many commercially available RLC extractors continue to make this assumption today. Users are placed at significant risk because they falsely believe the model is in some sense "broadband" or "wideband". It is a guess with no guarantee to be any better than any other assumed more distributed equivalent circuit for which there is no theoretical or physical justification. If one starts with AC data, assumes an equivalent circuit and *then* selects element values in such to fit the data then there is reason to argue this is a more valid model at higher frequencies. One cannot do this from only DC terminal-based data. Not that it's difficult, it is impossible. best regards, -Brad > -----Original Message----- > From: owner-ibis-users@eda.org > [mailto:owner-ibis-users@eda.org] On Behalf Of Scott McMorrow > Sent: Tuesday, May 31, 2011 5:04 PM > To: Ray Anderson > Cc: ibis-users; Ray Anderson > Subject: Re: [IBIS-Users] Requesting for some help / > information regarding the use of IBIS in SI simulation. > > Since the beginning of IBIS, the most accurate simulators > would turn the RLC package parasitics into a transmission > line equivalent. In lieu of any additional information it is > the most reasonable thing to do, since packages can be > approximated as transmission lines. > > > 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 > > TeraspeedR is the registered service mark of Teraspeed > Consulting Group LLC > > > On 5/31/2011 7:59 PM, Ray Anderson wrote: > > If you are using extracted RLC data to manually set up the package > > model you can certainly make intelligent decisions on the > topology of > > the model and the distribution of the RLC parasitics. > However if you > > are depending on a simulator to read the data from a IBIS > .pkg format > > file (or the [PIN] data) and set up a model for you then > your results > > may differ from simulator to simulator. > > > > -Ray > > Xilinx Inc. > > > > > > -----Original Message----- > > From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On > > Behalf Of Andrew Ingraham > > Sent: Tuesday, May 31, 2011 4:48 PM > > To: ibis-users > > Subject: Re: [IBIS-Users] Requesting for some help / information > > regarding the use of IBIS in SI simulation. > > > > Yes. > > > > I am usually tempted to start with an evenly distributed > RLC model ... > > unless I have reason to think that the distribution is > otherwise. For > > example, wirebonds might have most of the inductance and > resistance, > > whereas the leadframe may have more capacitance, which > might influence > > one to imbalance those factors unequally between die end > and pin end. > > But without hard data to back it up, that is just guessing. > > > > Andy > > > > -- > This message has been scanned for viruses and dangerous > content by MailScanner, and is believed to be clean. > > -------------------------------------------------------------------- > |For help or to subscribe/unsubscribe, e-mail 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 > - -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. - -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail 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: Wed, 01 Jun 2011 09:33:05 -0400 From: Scott McMorrow Subject: Re: [IBIS-Users] Requesting for some help / information regarding the use of IBIS in SI simulation. Brad It is certainly your prerogative to disagree with me. In the context of the original question, we are not talking about randomly distributed RLC, but rather package connections from board to silicon, which is the case in most IBIS models. Given that, we know the general topology. Whether the package uses lead frame, 2 layer FC packaging, 2/4 layer organic wire bond packaging, or multilayer buildup packaging, a single path from die to ball looks remarkably similar to cascaded transmission lines. Even bond wires look like transmission lines. If I'm given a single RLC for an IBIS model of a conventionally packaged silicon device , then I can guarantee you that the simulation will be more faithful to measurements when the transmission line equivalent is used, rather than lumped elements. Been there, done the measurements many, many times. When multiple sections are specified in the IBIS .pkg format, then there is no ambiguity, a non-zero RLC section length defines a distributed element, and a zero length section defines a lumped element. The simulator should model it as such. Having done correlation of package modeling to measurements from DC to 40 GHz on a 12-layer build-up with near zero error, I'm well aware of the issues involved with using the wrong modeling method, and poor material modeling. I agree with you that a single RLC is an extremely poor approximation of any complex package interconnect, or any interconnect for that matter. However, given that a user is presented with an RLC that was extracted with a quasi-static solver, as is the case with most IBIS models, I maintain that the result will be closer to reality when transformed into the distributed transmission line equivalent. I've seen way too many cases where simulators used a lumped RLC directly, grossly over predicting ringing at the die and in the channel, and confirmed by physical measurements. When we get into full-wave and hybrid full-wave AC modeling of packages there are a host of other issues that we can discuss, such as accurate dielectric modeling, accurate surface roughness modeling, as-designed vs. as-built package geometries, +/- 15% impedance variation due to manufacturing process and electromagnetic non-locality. But that is for another time. best regards, Scott 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 On 6/1/2011 1:53 AM, Brad Brim wrote: > hello Scott, > > I don't agree with you. Such simulators (or model extractors which write out > such "postprocessed" model data) are no more assured accurate than simply > applying or writing out the base RLC data. > > Most package extractors, especially ones you may refer to as applicable > "from the beginning", are based on static RLC simulation in which a single L > and C are extracted at exactly DC from two distinct simulations; > magnetostatic and electrostatic respectively. One has NO CLUE how to form > the equivalent circuit given only the static lumped L and C computed > independently. Of course, as asked and discussed by Ray, if the user has > insight from the physical structure then a more broadband model MIGHT be > generated, but there is no guarantee! > One person assuming a PI circuit (with the C split equally in half - or even > unequally - and the L in the middle) and another person assuming a TEE > circuit (with the L split and the shunt C in the middle) are no more correct > than the other. One has NO IDEA of the high frequency behavior of the > circuit (either just above the quasistatic limit where the likely spectral > content is relevant or higher where it is less likely relevant) without some > form of AC high-frequency simulation or measurement. The behavior at > "infinite" frequency in meaningless and to argue that a uniformly > distributed multi-stage ladder network is valid has no more justification > than another person arguing it should me a lowpass network with all the > inductance on the die side because of wirebond inductance. This argument has > blindly been accepted and argued for many years. It has been unjustified and > wrong, as you would say, "from the beginning". > > Want a valid model at higher frequencies, then extract AC information from > which to generate it. One's guess or intuitive argument without AC > information to back it up is only a guess, as Andy stated. The classical > uniformly distributed ladder network is a deceptively simple and intuitively > pleasing assumption that is easy to understand and unfortunately accepted by > way too many people in the industry. This supposed more accurate guess has > failed in too many cases and can even be worse than a simple totally > unbalanced low pass filter assumption over the frequency spectrum of > relevance. > > Many commercially available RLC extractors continue to make this assumption > today. Users are placed at significant risk because they falsely believe the > model is in some sense "broadband" or "wideband". It is a guess with no > guarantee to be any better than any other assumed more distributed > equivalent circuit for which there is no theoretical or physical > justification. > > If one starts with AC data, assumes an equivalent circuit and *then* selects > element values in such to fit the data then there is reason to argue this is > a more valid model at higher frequencies. One cannot do this from only DC > terminal-based data. Not that it's difficult, it is impossible. > > best regards, > -Brad > > >> -----Original Message----- >> From: owner-ibis-users@eda.org >> [mailto:owner-ibis-users@eda.org] On Behalf Of Scott McMorrow >> Sent: Tuesday, May 31, 2011 5:04 PM >> To: Ray Anderson >> Cc: ibis-users; Ray Anderson >> Subject: Re: [IBIS-Users] Requesting for some help / >> information regarding the use of IBIS in SI simulation. >> >> Since the beginning of IBIS, the most accurate simulators >> would turn the RLC package parasitics into a transmission >> line equivalent. In lieu of any additional information it is >> the most reasonable thing to do, since packages can be >> approximated as transmission lines. >> >> >> 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 >> >> TeraspeedR is the registered service mark of Teraspeed >> Consulting Group LLC >> >> >> On 5/31/2011 7:59 PM, Ray Anderson wrote: >>> If you are using extracted RLC data to manually set up the package >>> model you can certainly make intelligent decisions on the >> topology of >>> the model and the distribution of the RLC parasitics. >> However if you >>> are depending on a simulator to read the data from a IBIS >> .pkg format >>> file (or the [PIN] data) and set up a model for you then >> your results >>> may differ from simulator to simulator. >>> >>> -Ray >>> Xilinx Inc. >>> >>> >>> -----Original Message----- >>> From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On >>> Behalf Of Andrew Ingraham >>> Sent: Tuesday, May 31, 2011 4:48 PM >>> To: ibis-users >>> Subject: Re: [IBIS-Users] Requesting for some help / information >>> regarding the use of IBIS in SI simulation. >>> >>> Yes. >>> >>> I am usually tempted to start with an evenly distributed >> RLC model ... >>> unless I have reason to think that the distribution is >> otherwise. For >>> example, wirebonds might have most of the inductance and >> resistance, >>> whereas the leadframe may have more capacitance, which >> might influence >>> one to imbalance those factors unequally between die end >> and pin end. >>> But without hard data to back it up, that is just guessing. >>> >>> Andy >>> >> -- >> This message has been scanned for viruses and dangerous >> content by MailScanner, and is believed to be clean. >> >> -------------------------------------------------------------------- >> |For help or to subscribe/unsubscribe, e-mail 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 >> - -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. - -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail 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, 10 Jun 2011 12:30:07 +0530 From: "Ghatawade, Vinayak" Subject: [IBIS-Users] IV clamp range - --_000_B85A65D85D7EB246BE421B3FB0FBB593024D42652Ddbde02enttico_ Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Hello, I have question reagarding the IV sweep ranges used for IBIS IV table gener= ation. Cookbook does not have detailed sweep range for all corners specified expli= citly. The reason that I am asking this question is we have IV table which has cro= ss-overs for nom, strong and weak corners. In spice I see this behavior which is expected as per diode behavior since = the corners are temp variable as well. Weak will turn on (125c) first and then followed by nom (25) and strong (-4= 0c). This results in the crossover. Some customers are not willing to have these crossover (not sure why?). But= I feel since this is real behavior you should see the same reflected in the ibis model. Do you see a reason why IV crossovers are not allowed (recommended). I did = not see any checklist or parser giving out any warning /error due this this. Going back to the sweep voltage range when I see this crossover in spice (I= sweep voltages as mentioned in cookbook) and report the strong, weak to fi= t in the typical range voltage axis in the ibis model. Ex 1.8V IO below is the numbers that I use for IV sweep range. Sweep range that I use for typ - -1.8 to 3.6 Min/weak will be - -1.962 to 3.428 Max/strong will be - -1.602 to 3.798 Thanks vinayak - --=20 This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. - --_000_B85A65D85D7EB246BE421B3FB0FBB593024D42652Ddbde02enttico_ Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Hello,

      &n= bsp;            = ;

I have question reagarding the IV sweep ranges used for IBIS IV table generation.

Cookbook does not have detailed sweep range for all corners specified explicitly.

The reason that I am asking this quest= ion is we have IV table which has cross-overs for nom, strong and weak corners.=

In spice I see this behavior which is expected as per diode behavior since the corners are temp variable as well.=

Weak will turn on (125c) first and then followed by nom (25) and strong (-40c). This results in the crossover.

Some customers are not willing to have these crossover (not sure why?). But I feel since this is real behavior you should see the same

reflected in the ibis model.

 

Do you see a reason why IV crossovers = are not allowed (recommended). I did not see any checklist or parser giving out= any warning /error due this this.

 

Going back to the sweep voltage range = when I see this crossover in spice (I sweep voltages as mentioned in cookbook) a= nd report the strong, weak to fit in the

typical range voltage axis in the ibis model.

 

Ex 1.8V IO below is the numbers that I= use for IV sweep range.

 

Sweep range that I use for typ

-1.8 to 3.6 <= /p>

 

Min/weak will be

-1.962 to 3.428

 

Max/strong will be <= /font>

-1.602 to 3.798

 

 

Thanks

vinayak

 


--=20
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