[SI-LIST] Re: Resistor packs, SI issues?
- From: "Mike Greim" <mike.greim@xxxxxxxxxxx>
- To: <af@xxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Tue, 15 Nov 2005 09:36:26 -0600
Depending on the nature of the memory channel, for=20
instance, number of dimms, total ranks and the=20
distribution thereof, the viability of the interface
can be held together with for lack of a better phrase,
spit and scotch tape. It is therefore fairly common=20
for constraints to be employed that enhance noise margin.
Cross talk may be a contributing factor, but it is also
common for DQS to be packaged separately such that a
different termination scheme is desired. Not dis-similar
to requirements stating that address and control should
not be packaged with data.
You may also want to consider a different rpack size as
mfg cost may be increased due to the small size of the=20
package. Yes, I realize that there is a limited amount
of space to implement the termination scheme for this=20
channel
Best of luck.
Best Regards,
Michael Greim
Platform Engineering
Newisys, Inc.
512-634-0232 (V)
512-740-9097 (C)
We will either find a way or make one -Hannibal
Chance favors the prepared mind -Pasteur
The time is gone, the email's over
Thought I'd something more to say.......
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Anders Frederiksen
Sent: Tuesday, November 15, 2005 8:47 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Resistor packs, SI issues?
Hello All,
I've encountered a constraint on the signal allocation in resistor =
packs. The
application is a DDR-I interface. Frankly I was quite puzzled to see =
that Intel
specifically prohibit routing DQS (strobes) and other (ie. data mask) =
signal in one
respack!
If it weren't for the notes I'd never blink mixing <200MHz signals in =
respacks. I'm
using 0804 packs and fail to realize that cross talk could be a big =
problem here? Of
course the signals are raised from the reference plane and the =
horizontal spacing
between the signals is, say, double up for discrete resistors (or =
separate packs).
Is it the base material used in the packs that cause "issues"? Or am I =
completely
missing something??? I haven't been able to find any investigations =
regarding use of
respacks - so I'm very interested in hearing about your =
experiences/opinions!
Cheers,
Anders
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=20
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