[SI-LIST] Re: Coupled connector model
- From: "Scott McMorrow" <scott@xxxxxxxxxxxxx>
- Date: Thu, 03 Apr 2003 10:13:20 -0800
Dave,
The transformation is non-unique. For example, if you want to reduce
out 1 ground pin out of N total pins in the matrix, you are starting
with an NxN matrix and converting it to an (N-1)x(N-1) matrix. There
are a bunch of ways that you can make the reduction. You can assume no
net current flow in the ground pin (i.e. - the ground pin is an
equipotential surface). Of course, if the ground pin is identical to
all other pins in the design this is not true. There will be net
current flow due to crosstalk from the adjecent signals. Another
assumption that you can make is the direction of the current flow.
Unfortunately, this is dependent upon the the direction that the
neighbor pins are signalling. What you can do is to make 3 reductions.
In one assume that current flows through the ground pins in one
direction, in another assume that the current flows through in the
opposite direction, and in another assume that no net current flows.
This will give you three different matrices for the signal pins that
will come close to approximating the overall worst case behavior of the
connector. (These will not, however, show any of the dynamic behavior
that occurs under varied random switching patterns.)
This is, in my estimation, a lot of work and illustrates the problem
with board level signal integrity tools and their node 0, equipotential
ground assumption. Once you make that assumption, you eliminate an
additional mode of propagation from your circuits. If you do that for a
power pin and a ground pin, then you eliminate two additional modes.
You will never be able to simulate the dynamic variations that occur
under varied switching conditions after you have performed this type of
a reduction. The information is no longer there. All you can do is to
perform several transformations and simulate each separately.
Personally, I would always export this circuit to a spice-like simulator
that does not have the node 0 ground and power assumption. This kind of
brings us back full circle to the previous thread of yesterday:
* IBIS, si simulators, modeling and other sources of correlation error
Best regards,
scott
--
Scott McMorrow
Teraspeed Consulting Group LLC
2926 SE Yamhill St.
Portland, OR 97214
(503) 239-5536
http://www.teraspeed.com
David Fogel wrote:
>Hi,
>I have a coupled multi-line connector model that was generated by one of the
>leading connector vendor. It's in distributed RLC format. The coupling
>matrix treats all the pins equally, namely there are no pre-assigned ground
>pins. The model is suitable for Spice simulations where I can tie one side
>of the connector to ground 0 (through a small resistor) and keep the other
>side floating relative to ground node 0.
>Behavioral simulators do not allow for floating grounds. They treat both
>sides of the connector as ground reference. So I need to convert the
>multi-line matrix that I presently have into a new matrix that "understands"
>that certain pins are pre-assigned ground (their L,C values become 0).
>Any idea how to go about it, an algorithm or a script?
>Thanks
>David Fogel
>
>
>------------------------------------------------------------------
>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 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
>
>
>
>
--
Scott McMorrow
Teraspeed Consulting Group LLC
2926 SE Yamhill St.
Portland, OR 97214
(503) 239-5536
http://www.teraspeed.com
------------------------------------------------------------------
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 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:
