[SI-LIST] Re: DDR2 IMPEDANCE
- From: "Kai Keskinen" <kalevi@xxxxxxxxxx>
- To: <kenny_frohlich@xxxxxxxxx>, "tao xu" <helen.tao.xu@xxxxxxxxx>, <jory_mckinley@xxxxxxxxx>
- Date: Mon, 4 Dec 2006 17:37:36 -0500
I have seen very detailed application notes specifying varying impedances
from different memory controller vendors. I have simulated many of these,
taking into account impedance variations, and have found that it doesn't
matter that much between 40 to 60 Ohms for the single ended and 80 to 120
for the differential. If you have many DIMMs or DDR SDRAMs in series, you
should take into account the true distributed impedance due to the
capacitive loading at regular intervals of the DIMMs or SDRAMs. Whenever
possible, keep a single track on the same layer and keep all signals of a
byte lane on the same layer. DDR/DDR2 are actually very tolerant interfaces
if you do the analysis beforehand to find your acceptable limits.
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Kenny Frohlich
Sent: Sunday, December 03, 2006 11:57 AM
To: tao xu; jory_mckinley@xxxxxxxxx
Cc: kenny_frohlich@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: DDR2 IMPEDANCE
Hello Tao,
I'm interested in trace impedance on board.
I have always thought that the impedance of CLKs is 100 Ohms
(differential) and the impedance of other signals (DQ, DQM, DQS, Addr,
Commands) is 50 - 60 Ohms (single-ended). However, Intel, AMD, and SDRAM
vendors all specifies different impedance values so I got confused and posed
my questions. Also, I can not find any information on impedance in DDR2
standard spec.
Thanks,
Kenny
tao xu <helen.tao.xu@xxxxxxxxx> wrote:
for trace impedance. it is normally 50 or 60 ohm based on my previous
experince. Clock singal sometimes has lower impedance trace than other
signal groups.
On 12/1/06, tao xu wrote:
> kenny, what kind of impedance did you ask? Buffer output impedance for
> interface or normal trace impedance on board?
>
> On 12/1/06, Jory McKinley wrote:
> > Hello Kenny,
> > Are you designing this type interface? If so then take a look at the
AMCC spec:
> >
https://www.amcc.com/MyAMCC/retrieveDocument/PowerPC/440EP/PPC440EP_DS2002_v
1_24.pdf
> >
> > There should be some board guideline information for the DDR interface.
You will have to simulate.
> >
> > Simulating an existing interface? If you can obtain a board file then
the traces (impedances) can be extracted for the interface.
> >
> > -Jory
> >
> >
> > Kenny Frohlich wrote: Hi All,
> > Can someone please tell me where I can find information on DDR2
impedances (ie. what is the impedance of CLK? Data? Address? Command?)?
> > We use PowerPC PPC440EP and on-board DDR2 SDRAMs.
> > Thank you.
> >
> > Regards,
> > Kenny
> >
> > ---------------------------------
> > Access over 1 million songs - Yahoo! Music Unlimited.
> >
> > ------------------------------------------------------------------
> > 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
> >
> >
> >
> >
> >
> > ---------------------------------
> > Access over 1 million songs - Yahoo! Music Unlimited.
> >
> > ------------------------------------------------------------------
> > 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
> >
> >
> >
>
---------------------------------
Access over 1 million songs - Yahoo! Music Unlimited.
------------------------------------------------------------------
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:
