[SI-LIST] Re: FW: [IBIS-Users] Using IBIS models for VDD droop & Ground Bounce
- From: "Muranyi, Arpad" <arpad.muranyi@xxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Mon, 16 Jun 2003 08:30:21 -0700
Zhiping,
Other people beat me to answer your question. The reference
to the March 2002 paper is a good one, look at pg 3 in particular.
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=3D
-----Original Message-----
From: Zhiping Yang [mailto:zhiping@xxxxxxxxx]
Sent: Friday, June 13, 2003 1:56 PM
To: Muranyi, Arpad; si-list@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] FW: [IBIS-Users] Using IBIS models for VDD droop
& Ground Bounce
Hi Arpad,
I did not get your reply on 6/12/03. Maybe something is wrong with my =
mail
box. Thanks for reposting it!
Can you clarify why cross-bar current info is in the Vt curve? From my
understanding, the Vt curve only have the information about the current =
flow
out of the I/O pin, so I don't quite understand how the cross-bar =
current
could be included since it does not flow through the I/O pin. Certainly =
the
cross-bar current may has some impact on the current on I/O pin, but the
relationship should be very weak and it is very hard to estimate or =
extract
the cross-bar current accurately from Vt curve.
Your point about the C_comp is very valid and I totally aggree. Another
thing I did not mentioned in my previous e-mail is the difficulty for =
IBIS
model to include the on-die decaps from the decap cell or parasitic
capacitance. Since the IBIS model is extacted from ideal power supply
voltages, it is impossible to get the accurate decap info for the I/O =
cell
which plays very important role in SSO simulations.
In summary, the neglecting of cross-bar current makes the IBIS
under-estimate the SSO noise. On the other side, the neglecting of =
on-die
decap info makes the IBIS over-estimate the SSO noise, so there are =
still a
lot of work needed to make the IBIS model capable to simulation the SSO
noise correctly and accurately. Thanks.
Best regards,
Zhiping
----- Original Message -----
From: "Muranyi, Arpad" <arpad.muranyi@xxxxxxxxx>
To: <si-list@xxxxxxxxxxxxx>
Sent: Friday, June 13, 2003 1:28 PM
Subject: [SI-LIST] FW: [IBIS-Users] Using IBIS models for VDD droop & =
Ground
Bounce
> Zhiping,
>
> I replied on 6/12/2003 at 10:54 a.m. to ibis-users@xxxxxxxx
> Did you not get it? (See below)
>
> Arpad
>
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D=
3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D
>
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D=
3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D
> =3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D
>
> -----Original Message-----
> From: Muranyi, Arpad=3D20
> 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
>
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D=
3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D
>
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D=
3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D
> =
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=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 =
=3D
> very
> difficult to model the cross-bar current in IBIS model, but the =3D
> cross-bar
> current is very important for power delivery system simulation. About =
=3D
> one
> year ago, I did some simulation comparasions between HSPICE model and =
=3D
> IBIS
> model in power integrity. At that time, the IBIS model behaviored very =
=3D
> poor
> for some kinds of I/O buffer. I would be very interested to be updated =
=3D
> 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 =3D
> of
> CISCO Systems, Inc. and its affiliates and may be used only by the =
=3D
> intended
> recipient(s) of this communication for the purpose set forth and in a =
=3D
> 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 =3D
> 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
>
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D=
3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D
>
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D=
3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D
> =3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D
> >
> > -----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 =
=3D
> 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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