[SI-LIST] Re: FW: [IBIS-Users] Using IBIS models for VDD droop & Ground Bounce
- From: Ege Engin <engin@xxxxxxxxxx>
- To: arpad.muranyi@xxxxxxxxx
- Date: Sun, 15 Jun 2003 13:04:59 +0200
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=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
>
> -----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=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
>
> -----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=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
> >
> > -----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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