[SI-LIST] Re: Article discussion on bad packages
- From: steve weir <weirsp@xxxxxxxxxx>
- To: twesterh@xxxxxxxxx, <si-list@xxxxxxxxxxxxx>
- Date: Tue, 04 Jan 2005 09:29:05 -0800
Todd,
I advocate a little bit different specification than you on the
device. That is:
1) Device impedance profile up to 2X the cut-off frequency ( cut-off
determined using a hypothetical zero inductance attachment assumption ),
2) EITHER
a) device LPF equivalent lumped L-C-R, ( preferred ) or
b) Cut-off frequency and PCB maximum equivalent inductance from half to
twice the cut-off frequency
I have a couple of related slides prepared for my presentation next week at
the SVCEMC meeting.
The reason for wanting either a lumped equivalent L-C-R, or maximum PCB
inductance number is that if we model the package filter as a simple LC,
then the PCB inductance will appear in series and lower both the effective
cut-off frequency and the damping.
In most high performance designs, the PCB is going to look inductive at the
package cut-off frequency. So, 2b is just a simple derivation from the
information provided by 2a.
Even with FPGAs, this information would go a long way towards reducing
uncertainty and the need for test fixturing or prototyping to dial-in the
board level PDS.
What do you think?
Regards,
Steve.
At 11:54 AM 1/4/2005 -0500, Todd Westerhoff (twesterh) wrote:
>Happy New Year to all!
>
>Having gone through the collection of messages to this point, I have a few
>questions I'd like to raise:
>
>1) How are people accounting for the effects of on-die decoupling in their
>analyses? We can analyze the power delivery capbilities of the package, but
>part of the power delivery system is implemented by on-die decoupling, isn't
>it? How do folks go about extracting die parasitics and incorporating them
>into their PDS analyses?
>
>2) It seems to me that the combination of on-die and [optionally] on-package
>decoupling makes the package/die PDS self-sufficient above some frequency.
>If we look at the board PDS, the target PDS impedance requirements would
>therefore increase with frequency. The rolloff (or rollup, if you prefer)
>of target impedance with frequency would be design-specific, and, I believe,
>complex to determine, but would nonetheless serve as a design requirement
>for the board's PDS at that point.
>
>My question here - does anyone else think this would be a possible and
>reasonable method for documenting a chip's high speed current requirements?
>I suggest we leave FPGAs out for the moment, since their requirements will
>be design specific. Could we document PDS impedance/frequency profiles for
>standard components, and use that information to segregate some of the high
>speed signaling and PDS design tasks?
>
>Comments are welcome and appreciated.
>
>Todd.
>
>Todd Westerhoff
>High Speed Design Specialist
>Cisco Systems
>1414 Massachusetts Ave - Boxboro, MA - 01719
>email:twesterh@xxxxxxxxx
>ph: 978-936-2149
>============================================
>
>"Always do right.
> This will gratify some people and astonish the rest."
>
>- Mark Twain
>
>------------------------------------------------------------------
>To unsubscribe from si-list:
>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
>or to administer your membership from a web page, go to:
>//www.freelists.org/webpage/si-list
>
>For help:
>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>List FAQ wiki page is located at:
> http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>
>List technical documents are available at:
> http://www.si-list.org
>
>List archives are viewable at:
> //www.freelists.org/archives/si-list
>or at our remote archives:
> http://groups.yahoo.com/group/si-list/messages
>Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
>
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl?Si-List_FAQ
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
