[SI-LIST] Re: The case of 3 planes
- From: "databits" <databits@xxxxxxxxxxxxx>
- To: <rtso1@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Sat, 8 May 2004 17:54:18 -0500
I would also consider how "balanced" the return currents may or may not =
be
in the rest of the system.
Stated as a question: Are all of the return paths the same
physical/electrical length?
If not.. the return currents may not arrive at the same time at the =
return
planes that you modeled. If this is true, you may want to always keep =
a
full coupling matrix available. But if this is a singular, =
hypothetical,
one time only, will never be used to simulate a real system, let's test
theory question.... then you probably do not care about this point.
ap
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
On
Behalf Of xsirfr
Sent: Saturday, May 08, 2004 1:48 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] The case of 3 planes
Suppose I have 3 planes. I wish to create a LCR mesh element model for =
a
square section of the 3 planes. Now the inductance per square of plane =
is
the loop inductance per square, which can be expressed as a sum of =
Partial
inductances: self inductances - mutual inductances,=20
assuming currents flow
in opposite directions, which for a return path is a valid assumption. =20
Total Effective Inductance: L_loop =3D L11 + L22 - 2M (where =
M=3DL12=3DL21) For a
section comprised of 2 planes, the loop inductance is split in half and
applied to each "layer" of the schematic for the LCR model section. By
doing this, we don't need to use "K" factors for coupled inductors - we=20
simply model the net loop inductance as isolated inductors.
Now what is the correct inductance value for modeling plane#2 in a 3 =
plane
stack? Intuitively, the sandwiched layer should be modeled as having a
reduced value of inductance/sq, IF it uses both plane#1 and plane#3 as
return paths. But for a circuit that is powered between plane#1 and #2
only, it seems the inductance in plane#2 would be too small, since the
circuit does not use plane#3. My conclusion is that for a 3-plane =
system, I
CANNOT use isolated inductors, but have to use "K" factors to represent =
the
physical effect of coupled mutual inductance. This way, the total =
effective
loop inductance of either=20
adjacent pair (#1, #2) or (#2, #3) can be affected by the direction of
current in the other plane (#3 or #1). I believe I need to model K12 =
and
K23, but can ignor K13.
Is there a modeling expert out there that would concur with my =
conclusion?
Thanks,
-xsirfr
------------------------------------------------------------------
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: =20
//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
=20
------------------------------------------------------------------
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:
