[SI-LIST] Re: FW: [IBIS-Users] Using IBIS models for VDD droop & Ground Bounce
- From: Wen Fred-Q16099 <fred.wen@xxxxxxxxxxxx>
- To: "'engin@xxxxxxxxxx'" <engin@xxxxxxxxxx>, arpad.muranyi@xxxxxxxxx
- Date: Mon, 16 Jun 2003 12:03:25 +0800
Hi Ege,
In terms of SSN, I think you could simulate the effect of the IO buffer by
introducing 3-conductor models into IBIS. But, I think Zhiping's concern is
related to the switching current in power system led by the fastly switching
core logic which he mentioned by cross-bar. And that is also mine. Believe not
all the AC current in power system is directly from IO circuit of components.
How do you get the information of the rest, say, the cross-bar?
Could you advise?
Regards,
Fred
> -----Original Message-----
> From: Ege Engin [mailto:engin@xxxxxxxxxx]
> Sent: Sunday, June 15, 2003 7:05 PM
> To: arpad.muranyi@xxxxxxxxx
> Cc: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: FW: [IBIS-Users] Using IBIS models for
> VDD droop & Ground Bounce
>
>
> Zhiping,
> There were some presentations about Power/Ground noise issues
> in several
> IBIS summit meetings, including mine:
>
> Three-Conductor Modeling of Power/Ground Noise:
> http://www.eda.org/pub/ibis/summits/mar03/engin.pdf
> Power/Gnd Simulation:
> http://www.eda.org/pub/ibis/summits/sep01/raghuram.pdf
> SSN: http://www.eda.org/pub/ibis/summits/jan00/unger.zip
>
> Simulations including Power/Ground noise is in principle possible with
> IBIS models (e.g., HSpice B-element has an option to adjust
> it). Besides
> the splitting of the C_comp value, which Arpad explained in
> detail, two
> more points are relevant for a Power/Ground simulation:
> - Pin Mapping is needed to associate each I/O buffer with its
> corresponding supply bus
> - Parasitics on the power supply distribution has to be
> included in the
> package model
>
> I didn't check the accuracy of IBIS models for Power/Ground noise
> analysis. I think this is still an open issue, which needs further
> investigations.
>
> I hope this helps,
>
> Ege
>
>
>
>
> "Muranyi, Arpad" schrieb:
> >
> > Zhiping,
> >
> > I replied on 6/12/2003 at 10:54 a.m. to ibis-users@xxxxxxxx
> > Did you not get it? (See below)
> >
> > Arpad
> >
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3
> D=3D=3D=3D=3D=
> >
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3
> D=3D=3D=3D=3D=
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D
> >
> > -----Original Message-----
> > From: Muranyi, Arpad=20
> > Sent: Thursday, June 12, 2003 10:54 AM
> > To: ibis-users@xxxxxxx
> > Subject: RE: [IBIS-Users] Using IBIS models for VDD droop & Ground
> > Bounce
> >
> > Zhiping,
> >
> > I am sorry, but I do not have any presentations on this subject.
> > Regarding crow-bar currents, IBIS will do it fairly well, this
> > information is included in the shape of the Vt curves (waveforms).
> > However, depending on the tool's algorithm you may not necessarily
> > get perfect results.
> >
> > The accuracy of such simulations will also depend on how the
> > C_comp value is split up in the IBIS model. If you have only
> > one cap between pad and GND, you cannot do accurate power
> > delivery simulations, because the actual device has at least
> > two of these, one to GND and another one to Vcc. In earlier
> > versions of HSPICE, they used to connect the C_comp to node
> > zero (ideal GND) which meant the current of the capacitance
> > never went through the power/GND nodes. This has been fixed a
> > long time ago, but you need to know about it. Maybe other tools
> > do it too(?).
> >
> > I hope this helps,
> >
> > Arpad
> >
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3
> D=3D=3D=3D=3D=
> >
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3
> D=3D=3D=3D=3D=
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> >
> > -----Original Message-----
> > From: Zhiping Yang [mailto:zhiping@xxxxxxxxx]
> > Sent: Tuesday, June 10, 2003 10:09 AM
> > To: Muranyi, Arpad; ibis-users@xxxxxxx
> > Subject: Re: [IBIS-Users] Using IBIS models for VDD droop & Ground
> > Bounce
> >
> > HI Arpad,
> >
> > Can you clarify a little bit more on this? Do you have any papers or
> > presenations on this topic? For my understanding, it is
> impossible or =
> > very
> > difficult to model the cross-bar current in IBIS model, but the =
> > cross-bar
> > current is very important for power delivery system
> simulation. About =
> > one
> > year ago, I did some simulation comparasions between HSPICE
> model and =
> > IBIS
> > model in power integrity. At that time, the IBIS model
> behaviored very =
> > poor
> > for some kinds of I/O buffer. I would be very interested to
> be updated =
> > on
> > new IBIS capabilities on power delivery system simulations. Thanks.
> >
> > Zhiping
> >
> > Zhiping Yang. Ph.D.
> > Signal Integrity Engineer
> > CISCO SYSTEMS
> > 170 West Tasman Dr.
> > San Jose, CA 95134
> > Phone: 408-525-5690
> > Fax: 408-525-5690
> > E-mail: zhiping@xxxxxxxxx
> >
> > This Message and any attached documents contain
> confidential information =
> > of
> > CISCO Systems, Inc. and its affiliates and may be used
> only by the =
> > intended
> > recipient(s) of this communication for the purpose set
> forth and in a =
> > manner
> > consistent with your agreement with Cisco Systems, Inc. to
> preserve its
> > confidential information.
> >
> > ----- Original Message -----
> > From: "Muranyi, Arpad" <arpad.muranyi@xxxxxxxxx>
> > To: <ibis-users@xxxxxxx>
> > Sent: Tuesday, June 10, 2003 9:43 AM
> > Subject: RE: [IBIS-Users] Using IBIS models for VDD droop & Ground =
> > Bounce
> >
> > > John,
> > >
> > > Sorry for the late reply. We do use IBIS models for what we
> > > call "Power Delivery" simulations (which is the same thing
> > > you asked about). However, we only use the buffer model in
> > > IBIS format, and have a more accurate package and PDN model
> > > in different formats.
> > >
> > > The new ICM (IBIS Interconnect Model Specification) provides
> > > (now) a much more accurate way to model the passive circuits,
> > > but the new language extensions to the buffer modeling
> > > capabilities of IBIS (BIRD75) will provide further improvements
> > > for buffer modeling also.
> > >
> > > As soon as tools begin to support these new features we will be
> > > able to do very accurate power delivery simulations using IBIS
> > > files for the passive as well as the active circuits.
> > >
> > > Arpad Muranyi
> > > Intel Corporation
> > > =
> >
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3
> D=3D=3D=3D=3D=
> >
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3
> D=3D=3D=3D=3D=
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> > >
> > > -----Original Message-----
> > > From: John Phillippe [mailto:john.phillippe@xxxxxxxxxxxx]
> > > Sent: Thursday, May 08, 2003 2:27 PM
> > > To: ibis-users@xxxxxxx
> > > Subject: [IBIS-Users] Using IBIS models for VDD droop &
> Ground Bounce
> > >
> > >
> > > I'm curious as to how many people use IBIS models to
> simulate VDD =
> > Droop
> > > and Ground Bounce. Is IBIS even a worthwhile format to
> try this with?
> > > Do current simulators do anything with regards to
> modeling the voltage
> > > drops across the powerbus on the chip?
> > >
> > > --
> > > John Phillippe
> > > SPS, 32 Bit Embedded Controller Division, IC Creation
> > > Motorola - 512-895-1835
> > > Austin, TX - john.phillippe@xxxxxxxxxxxx
> > >
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