[SI-LIST] Re: DDR2 2-slot design preference...
- From: olaney@xxxxxxxx
- To: leeritchey@xxxxxxxxxxxxx
- Date: Mon, 29 Oct 2007 11:04:39 -0700
Thank you, Lee. I'm skeptical of simulations that ignore the damping
effect of the nonlinear loads created by populating the board with
integrated circuits. We've all seen ground planes rattle, but I've
never seen a problem traceable to cavity resonance between planes. A
real world example would be welcome.
Orin
On Mon, 29 Oct 2007 10:09:28 -0700 "Lee Ritchey"
<leeritchey@xxxxxxxxxxxxx> writes:
> I have heard many times about cavity resonances between power and
> ground
> planes being the source of problems. However, I have yet to see any
> clear
> proof that such things happen and I have never seen a product fail
> from
> this in the design of 3000+ PCBs. Could those who claim this
> happens
> please supply some evidence of this? Not simulations, but actual
> measured
> results and not a statement that the last place it happened was at a
> client
> who has an NDA in place that prevents revealing the data.
>
> Lee Ritchey
>
>
> > [Original Message]
> > From: steve weir <weirsi@xxxxxxxxxx>
> > To: <Monji.Jabori@xxxxxx>
> > Cc: <si-list@xxxxxxxxxxxxx>
> > Date: 10/27/2007 2:09:16 PM
> > Subject: [SI-LIST] Re: DDR2 2-slot design preference...
> >
> > Jabori, the issue in each case will be the resonant frequency of
> the GND
> > - GND cavity. Stitch the cavity with an adequate via density to
> get the
> > resonance well above your signal energy and either topology can be
> made
> > to work well.
> >
> > Steve.
> > Jabori, Monji wrote:
> > > Hi Experts,
> > >
> > >
> > > I am looking at two designs for a 2-slot DDR2-800 memory system.
> One is
> > > a butterfly design and the other has the slot on opposite sides
> of the
> > > motherboard (top and bottom).
> > >
> > > I am looking at the GND reference for both designs and have the
> > > following question knowing that I have to use GND referenced
> layers for
> > > each DDR2 channel.
> > >
> > >
> > >
> > > For a butterfly design, my traces on an 8-layer design will flow
> from
> > > the memory controller via 2 internal layers with 2 different GND
> layers,
> > > i.e., one slot will have to change GND reference while the other
> will
> > > not.
> > >
> > >
> > >
> > > In an opposite 2-slot design, however, we can make the traces
> that go to
> > > each internal layer have the same GND reference as the DIMM that
> is
> > > closer to it. For example, the Top DIMM will have the same GND
> reference
> > > (L2) as its channel traces coming on L3 while the Bottom DIMM
> will have
> > > its GND reference (L7) as its channel traces coming on L6.
> > >
> > >
> > >
> > > Having said the above, would you guys prefer one design over
> another
> > > from an Signal Integrity point of view??
> > >
> > >
> > >
> > > Thanks in advance.
> > >
> > >
> > >
> > > Monji
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> ------------------------------------------------------------------
> > > 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 technical documents are available at:
> > > http://www.si-list.net
> > >
> > > 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
> > >
> > >
> > >
> > >
> > >
> >
> >
> > --
> > Steve Weir
> > Teraspeed Consulting Group LLC
> > 121 North River Drive
> > Narragansett, RI 02882
> >
> > California office
> > (408) 884-3985 Business
> > (707) 780-1951 Fax
> >
> > Main office
> > (401) 284-1827 Business
> > (401) 284-1840 Fax
> >
> > Oregon office
> > (503) 430-1065 Business
> > (503) 430-1285 Fax
> >
> > http://www.teraspeed.com
> > This e-mail contains proprietary and confidential intellectual
> property
> of 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:
> > //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:
> > //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 technical documents are available at:
> http://www.si-list.net
>
> 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 technical documents are available at:
http://www.si-list.net
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:
