[SI-LIST] Re: [SPAM] Re: Question about split gnd planes
- From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
- To: "esayre@xxxxxxxx" <esayre@xxxxxxxx>, joel@xxxxxxxxxx
- Date: Tue, 30 May 2006 11:21:55 -0700
Apple has a flock of patents like this and a band of lawyers that like to
sue over them. A couple of years agoa, I was involved in one of those
suits over the practice of splid Vdd planes to put more than one voltgae
in a single plane. Apple lost of course. Seems they have a group of
people patenting most anything, probable air in the bargain!
> [Original Message]
> From: <esayre@xxxxxxxx>
> To: <joel@xxxxxxxxxx>
> Cc: <manickavelu_m@xxxxxxxxxxxx>; <istvan.novak@xxxxxxxxxxx>; Ed Troy
<etroy@xxxxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>; <weirsi@xxxxxxxxxx>
> Date: 5/30/2006 10:19:19 AM
> Subject: [SI-LIST] Re: [SPAM] Re: Question about split gnd planes
>
> All:
>
> Please look into the patent apple claims to own for caps across split
> planes. I haven't read anywhere that apple patent attorney's have said
> its OK to violate their patent.
>
> This is just another examp-le of poor review of patents and the abuse of
> simp0le but effective fixes that should be available to all. I am sure
> there is prior art which would make this patent unenforcable.
>
> ed
> ==========
> Dr. Edward P. Sayre, P. E.
> North East Systems Associates, Inc.
> 1 South Avenue, 3rd Floor
> Natick, MA 01760
> [T] 508-652-0088
> [F] 508-652-0083
>
>
> > -------- Original Message --------
> > Subject: [SPAM] [SI-LIST] Re: Question about split gnd planes
> > From: Joel Brown <joel@xxxxxxxxxx>
> > Date: Tue, May 30, 2006 9:26 am
> > To: weirsi@xxxxxxxxxx
> > Cc: manickavelu_m@xxxxxxxxxxxx, istvan.novak@xxxxxxxxxxx, Ed Troy
> > <etroy@xxxxxxxxxxxxxxx>, si-list@xxxxxxxxxxxxx
> >
> > This is similar to a question I posted about an Intel app note for an
> > Ethernet controller that recommended a plane split between the
controller
> > andEthernet connector with built in magnetics. Intel also suggested that
> > capsof various values might be needed to bridge across the split which
would
> > seem to negate the purpose of the split. Our EMI consultant said do not
use
> > aplane split. Most responses I got back said the plane split was
necessary
> > toprevent common mode noise on the ground plane from coupling across the
> > Ethernet magnetics which are designed to attenuate common mode noise. I
also
> > had a thought to eliminate ground planes around the Ethernet connector
> > excepton the bottom layer of the board thinking there would be less
coupling
> > from the bottom of the board to the Ethernet connector. My
understanding of
> > plane splits is this: a plane split is a slot antenna, there is likely
to be
> > an RF potential with respect to the ground planes on either side of the
> > splitwhich energizes the antenna and causes radiation. This can be
mitigated
> > by bridging across the plane split with capacitors at intervals which
are
> > small compared to the wavelength of the noise on the planes. This is
more
> > commonly done with plane splits where the DC voltages of the planes are
at
> > different potentials.
> > Joel
> >
> >
> > steve weir wrote: Manix, no. There are many misconceptions out there
about
> > the myth of ground and its relation to noise isolation. Those myths get
> > propagated into misguided applications of moats and such. Think in
fields
> > andthe misconceptions go away. Steve. At 09:50 PM 5/25/2006,
Manickavelu M.
> > wrote: Istan, Is it not that the analog and digital grounds planes can
not
> > beconnected together anywhere but only under the chip that sources the
> > analogsignals? Also that while coupling these two planes we should not
use
> > direct Cu plane connection but couple them via inductors? Manix,
MindTree.
> > -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx[1]
> > [mailto:si-list-bounce@xxxxxxxxxxxxx[2]] On Behalf Of
> > istvan.novak@xxxxxxxxxxx[3] Sent: Friday, May 26, 2006 6:26 AM To: Ed
Troy;
> > si-list@xxxxxxxxxxxxx[4] Subject: [SI-LIST] Re: Question about split gnd
> > planes Ed, Splitting more than one ground plane in the stackup requires
a
> > lotof consideration, and mostly it is not necessary. Isolating a
sensitive
> > circuit (e.g., analog input, low-jitter oscillator) may be a good idea,
but
> > instead of cutting a large solid ground plane, you may want to try
first to
> > put the circuit to be isolated on a grounded patch on a 'non-ground'
layer.
> > You can make ground surface patches under and around your circuit to be
> > isolated, or you can put the patch on a signal layer. Regards, Istvan
Novak
> > SUN Microsystems From: Ed Troy <etroy@xxxxxxxxxxxxxxx>[5] Date: Thu May
25
> > 15:38:33 CDT 2006 To: si-list@xxxxxxxxxxxxx[6] Subject: [SI-LIST]
Question
> > about split gnd planes If you have a circuit board that requires a
split gnd
> > plane over a small section of the board, and you have several ground
planes,
> > should only one have the split (the one nearest the side containing the
> > components that require analog ground) while the rest of the ground
planes
> > are continuous, or should the split section be on all ground layers? I
would
> > think that you should only have it on one layer. Also, if it should
only be
> > on one layer, I would imagine it would be best to connect it to the
digital
> > ground with one, and only one, via. Is that generally correct? What are
some
> > good references for layer stackups, etc? I know I saw one, once, but
can't
> > remember where. Ed
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