In line ... -joel
Ali Ghiasi wrote:
Joel
Joel Goergen wrote:
Ali,
We have been focusing on this for several months now. I think Steve
has presented nothing new that hasn't been published and, at a min,
agreed to in some form of straw poll.
I am not disagreeing that these were agreed in
the straw poll, I just didn't participated in some
of earlier meeting.
I would like to offer a thought ...
For the channel ... we use the SMA and SMA foot print that allows for a
clean launch. At both ends of the channel. This allows us to see the
SDD11/SDD22 without doing a major de-embedding and still allow for freq
to 12.5Ghz.
How can you define a channel "backplane" but
not
define a minimum attribute for the connector.
There is no reason to de-embed the connector as the connector is part
of the channel. A compliant
channel must meet an specified transmission and reflection property
which include connector.
Ali, The connector is not the issue. It never
has been the major contributor. The thru-hole or SMT pad for the
connector has, as well as the pin depth pressed into the hole. The
channel model and the test cards defined takes that into account.
-joel
For the tp1 and tp4 ... we then let the tx (tp1) handle the BGA and
via, the rx(tp4) handle the via, both cap pads, both via and BGA pad.
It will be easier to do the de-embedding and specify the SDD11/SDD22 as
seen by the chip from the channel.
The methodology specified currently in BP is
suitable for chip to chip applications but not for backplane.
Where do you handle connector effect and multiple reflection between
the connector-IC? In 4Gig FC we addressed some of these issues and do
specify the channel which include the connector.
Ali, There has been data presented to discuss
daughter card channel lengths, as well as teh back plane portion of the
total length. What you are getting at is a channel that varies with
thru-hole location. It's not a factor of thru-hole location as much as
it is a stub length. I could not be talked into a variable model when
the issue you are describing can, in most cases, be delt with in design
practises.
-joel
Thanks,
Ali
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