[SI-LIST] Re: PDS analysis?

Ivor, you can find examples in papers by people like Larry, Istvan, and=20
books that are out there.  But, I am not sure where you are going with=20
this.  Since terms like "well fed" are ambiguous, I don't know what=20
example you are looking for or to what purpose.  My sense is that you=20
have a belief that if one follows some ambiguous "industry practices"=20
that the PDN will usually "work fine".  Undefined engineering leads to=20
undefined results.  If you want predictable results then:  Define the=20
requirements and engineer to them.=20

We can characterize components to determine their actual power delivery=20
requirements.  Once known we can easily demonstrate failures that result =

when we don't meet those requirements.  It is also easy to demonstrate=20
what different PDN practices do to the impedance profile under any=20
particular set of controlled circumstances we wish to create.

If you want to see resonance effects for yourself then:  Design some=20
board following one of the popular ad-hoc rules.  If for example you=20
design a board with one 0402 capacitor every two square inches and the=20
plane cavity is 4mil FR406 on layers 2/3, the bypass to cavity PRF will=20
land around 330MHz depending on how you do your vias. If the planes are=20
deeper in the board that frequency will just go down.  Then get yourself =

a programmable clock generator and use it to drive some device like a=20
PLD or FPGA with a bunch of outputs simultaneously in a simple 1-0-1-0=20
sequence while you monitor the power supply planes with a decent scope.  =

Just step frequency until the bit rate / 2 excites the lowest parallel=20
resonance in the power system.  After that experiment see if your=20
feelings about what works fine are still the same.

Steve

Bowden, Ivor wrote:
> Hi Gil,
> =20
>
> Thanks for sharing.
>
> =20
>
> By "real world" I do not mean rules of thumb and shortcuts, I mean exam=
ples. I expect that most folks on this list, especially those for whom SI=
 is primary activity, can demonstrate examples of operational failures du=
e to bad board layout. I also know that a large number of designs never g=
et PDS analysis, yet work fine. I'm interested in typical modern technolo=
gy designs that are laid out in standard industry practice: contiguous gr=
ound planes, tandem heavy split power planes not used as return reference=
, plenty of properly located bypass caps, etc that have operational failu=
res which could have been pre-determined by PDS analysis, and if so, how =
did that operational failure manifest? For example, it would be interesti=
ng to see a scope (or simulation) snap shot of the voltage measured direc=
tly across vias to contiguous well fed planes as a device current require=
ment approaches the planes resonant frequency. And I mean a real device, =
not a hypothetical entity tuned to instigat
>  e the problem.
>
> =20
>
> -Ivor
>
> =20
>
> -----Original Message-----
> From: Gil Simsic [IEEE] [mailto:gsimsic.ieee@xxxxxxxxxxxxx]=20
> Sent: Friday, March 28, 2008 1:08 PM
> To: Bowden, Ivor; si-list@xxxxxxxxxxxxx
> Subject: Re: [SI-LIST] Re: PDS analysis?
>
> =20
>
> Ivor
>
> =20
>
> I am involved in design since 1993, and have numerous of successful des=
igns=20
>
> under my belt. (I know - not very humble...)
>
> =20
>
> In one way or another I worked and learned from SI leaders (aka - gurus=
)=20
>
> like Lee Ritchey, Istvan Novak, Eric Bogatin, Scott McMorrow and Howard=
=20
>
> Johnson (and others that due to a senior moment I did not mention here =
-=20
>
> sorry) I gratefully owe my knowledge to them.
>
> =20
>
> by the way - all I tried to do is to learn about "real world picture".
>
> =20
>
> My greatest lesson is - there are no short cuts and no rule of thumbs. =
I=20
>
> read daily emails on this list that prove this point over and over agai=
n.
>
> =20
>
> And than again I might misunderstand you...
>
> If the by 'real world' you refer to 'rules of thumbs' and 'short cuts',=
 I=20
>
> will strongly recommend you to shy away from that 'real world'. I reall=
y=20
>
> think that any design as hypothetic or rhetorical as it is, needs analy=
sis=20
>
> (the subject of your email is PDS analysis...).
>
> =20
>
> Most of the SI phenomena are frequency depended.
>
> =20
>
> You said - * I'm more interested in answers like "you might see a wavef=
orm=20
>
> of xxx characteristics across the bypass capacitor". *
>
> My answer - "you might see a waveform of xxx characteristics across the=
=20
>
> bypass capacitor". ;-)
>
> How can one attempt giving you any 'ball-park' numbers for a frequency =

>
> dependent component with out knowing what the frequency parts are?
>
> =20
>
> Good luck!
>
> =20
>
> Gil
>
> ----- Original Message -----=20
>
> From: "Bowden, Ivor" <ibowden@xxxxxxxxxxxxxxxxx>
>
> To: <si-list@xxxxxxxxxxxxx>
>
> Sent: Friday, March 28, 2008 12:11 PM
>
> Subject: [SI-LIST] Re: PDS analysis?
>
> =20
>
> =20
>
>  =20
>> Hi,
>>    =20
>
>  =20
>
>  =20
>
>  =20
>> I'd like to thank everyone who replied so far, off and on the list. I =

>>    =20
>
>  =20
>> emphasize that this is a rhetorical question, it doesn't represent any=
=20
>>    =20
>
>  =20
>> specific product. I also emphasize that I'm interested more in the "re=
al=20
>>    =20
>
>  =20
>> world observation" part. Instead of answers like "your power plane may=
=20
>>    =20
>
>  =20
>> have a resonance at xxx frequency", I'm more interested in answers lik=
e=20
>>    =20
>
>  =20
>> "you might see a waveform of xxx characteristics across the bypass=20
>>    =20
>
>  =20
>> capacitor". Also, this question is more about power distribution than =

>>    =20
>
>  =20
>> signal return path. All answers appreciated.
>>    =20
>
>  =20
>
>  =20
>
>  =20
>
>  =20
>> -Ivor
>>    =20
>
>  =20
>
>  =20
>
>  =20
>
>  =20
>> ________________________________
>>    =20
>
>  =20
>
>  =20
>> From: Bowden, Ivor
>>    =20
>
>  =20
>> Sent: Friday, March 28, 2008 7:24 AM
>>    =20
>
>  =20
>> To: si-list@xxxxxxxxxxxxx
>>    =20
>
>  =20
>> Subject: PDS analysis?
>>    =20
>
>  =20
>
>  =20
>
>  =20
>
>  =20
>> Hi SI Experts,
>>    =20
>
>  =20
>
>  =20
>
>  =20
>
>  =20
>> Say you have a typical PCB with modern technology mix of CPU, DSP, DDR=
,=20
>>    =20
>
>  =20
>> GIGE, PCIE, etc. Say it is a multi-layer stackup in the form of=20
>>    =20
>
>  =20
>> GND-SIG-SIG-GND sets, with the power distribution centered in the stac=
kup=20
>>    =20
>
>  =20
>> as solid ground plane - split power plane - split power plane - solid =

>>    =20
>
>  =20
>> ground plane, using 1oz copper and 3.5 mil dielectric. Assuming the sp=
lit=20
>>    =20
>
>  =20
>> power planes utilize sufficient area to keep the point to point induct=
ance=20
>>    =20
>
>  =20
>> and resistance to reasonable values, and 0.1uF ceramic bypass caps are=
=20
>>    =20
>
>  =20
>> evenly placed at device pins, and bulk capacitance is placed as needed=
,=20
>>    =20
>
>  =20
>> would there be reason to expect any problems, such as plane resonance,=
=20
>>    =20
>
>  =20
>> etc? If so, what would be the observable real world manifestations, in=
=20
>>    =20
>
>  =20
>> terms of circuit performance and power pins scope waveforms? Would the=
re=20
>>    =20
>
>  =20
>> be significant advantage to analyzing this PDS, or should following th=
is=20
>>    =20
>
>  =20
>> "industry standard practice" for PCB PDS be sufficient to expect robus=
t=20
>>    =20
>
>  =20
>> behavior?
>>    =20
>
>  =20
>
>  =20
>
>  =20
>
>  =20
>> Thanks,
>>    =20
>
>  =20
>
>  =20
>
>  =20
>
>  =20
>> Ivor Bowden
>>    =20
>
>  =20
>
>  =20
>> Senior Hardware Engineer
>>    =20
>
>  =20
>
>  =20
>> Curtiss-Wright Controls Embedded Computing
>>    =20
>
>  =20
>
>  =20
>> 10201 Wateridge Circle
>>    =20
>
>  =20
>
>  =20
>> Suite 300
>>    =20
>
>  =20
>
>  =20
>> San Diego, CA 92121
>>    =20
>
>  =20
>
>  =20
>> 858-452-0020 x 4405
>>    =20
>
>  =20
>
>  =20
>> ibowden@xxxxxxxxxxxxxxxxx
>>    =20
>
>  =20
>
>  =20
>
>  =20
>
>  =20
>
>  =20
>> ______________________________________________________________________=
_
>>    =20
>
>  =20
>> This e-mail and any files transmitted with it are proprietary and inte=
nded=20
>>    =20
>
>  =20
>> solely for the use of the individual or entity to whom they are addres=
sed.=20
>>    =20
>
>  =20
>> If you have reason to believe that you have received this e-mail in er=
ror,=20
>>    =20
>
>  =20
>> please notify the sender and destroy this email and any attached files=
=2E=20
>>    =20
>
>  =20
>> Please note that any views or opinions presented in this e-mail are so=
lely=20
>>    =20
>
>  =20
>> those of the author and do not necessarily represent those of the=20
>>    =20
>
>  =20
>> Curtiss-Wright Corporation or any of its subsidiaries.  Documents atta=
ched=20
>>    =20
>
>  =20
>> hereto may contain technology subject to government export regulations=
=2E=20
>>    =20
>
>  =20
>> Recipient is solely responsible for ensuring that any re-export, trans=
fer=20
>>    =20
>
>  =20
>> or disclosure of this information is in accordance with applicable=20
>>    =20
>
>  =20
>> government export regulations.  The recipient should check this e-mail=
 and=20
>>    =20
>
>  =20
>> any attachments for the presence of viruses. Curtiss-Wright Corporatio=
n=20
>>    =20
>
>  =20
>> and its subsidiaries accept no liability for any damage caused by any =

>>    =20
>
>  =20
>> virus transmitted by this e-mail.
>>    =20
>
>  =20
>> ------------------------------------------------------------------
>>    =20
>
>  =20
>> To unsubscribe from si-list:
>>    =20
>
>  =20
>> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>>    =20
>
>  =20
>
>  =20
>> or to administer your membership from a web page, go to:
>>    =20
>
>  =20
>> http://www.freelists.org/webpage/si-list
>>    =20
>
>  =20
>
>  =20
>> For help:
>>    =20
>
>  =20
>> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>>    =20
>
>  =20
>
>  =20
>
>  =20
>> List technical documents are available at:
>>    =20
>
>  =20
>>                http://www.si-list.net
>>    =20
>
>  =20
>
>  =20
>> List archives are viewable at:
>>    =20
>
>  =20
>> http://www.freelists.org/archives/si-list
>>    =20
>
>  =20
>> or at our remote archives:
>>    =20
>
>  =20
>> http://groups.yahoo.com/group/si-list/messages
>>    =20
>
>  =20
>> Old (prior to June 6, 2001) list archives are viewable at:
>>    =20
>
>  =20
>>  http://www.qsl.net/wb6tpu
>>    =20
>
>  =20
>
>  =20
>
> =20
>
>
> _______________________________________________________________________=

> This e-mail and any files transmitted with it are proprietary and inten=
ded solely for the use of the individual or entity to whom they are addre=
ssed. If you have reason to believe that you have received this e-mail in=
 error, please notify the sender and destroy this email and any attached =
files. Please note that any views or opinions presented in this e-mail ar=
e solely those of the author and do not necessarily represent those of th=
e Curtiss-Wright Corporation or any of its subsidiaries.  Documents attac=
hed hereto may contain technology subject to government export regulation=
s. Recipient is solely responsible for ensuring that any re-export, trans=
fer or disclosure of this information is in accordance with applicable go=
vernment export regulations.  The recipient should check this e-mail and =
any attachments for the presence of viruses. Curtiss-Wright Corporation a=
nd its subsidiaries accept no liability for any damage caused by any viru=
s transmitted by this e-mail.
> ------------------------------------------------------------------
> 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:
> http://www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>
> List technical documents are available at:
>                 http://www.si-list.net
>
> List archives are viewable at:    =20
>               http://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
>  =20
>
>
>  =20


--=20
Steve Weir
Teraspeed Consulting Group LLC=20
121 North River Drive=20
Narragansett, RI 02882=20

California office
(408) 884-3985 Business
(707) 780-1951 Fax

Main office
(401) 284-1827 Business=20
(401) 284-1840 Fax=20

Oregon office
(503) 430-1065 Business
(503) 430-1285 Fax

http://www.teraspeed.com
This e-mail contains proprietary and confidential intellectual property o=
f Teraspeed Consulting Group LLC
-------------------------------------------------------------------------=
-----------------------------
Teraspeed(R) is the registered service mark of Teraspeed Consulting Group=
 LLC


------------------------------------------------------------------
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:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field


List technical documents are available at:
                http://www.si-list.net

List archives are viewable at:     
                http://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: