[SI-LIST] Re: [SPAM] Re: Question about split gnd planes
- From: <jose_moreira@xxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Tue, 30 May 2006 19:45:29 +0200
On the other side one has to remember that one of the main reasons to =
have a large portfolio of patents is to protect against other companies =
trying to sue you.
I don't expect Apple to start asking for money to each company that uses =
caps across split planes (independent of the question if the patent is =
even valid, that is for the courts to decide), but I do expect that if =
Apple gets sued by some guy that wants money for some technique they use =
on the PCB boards of their latest laptops (because it is more profitable =
suing Apple than some OEM in Asia), that they can go to their patent =
portfolio and use any weapon (patent) they have to fight the guy.
It is preferable to have 1000 patents (where probably at the end only 2 =
are real patents that we (down to earth engineers) would consider worthy =
of a patent) than only 2 patents, when you are being sued by a someone.
This does not mean that I think the current patent system is OK :).
Just a thought.
_____________________________________________________
Jose Moreira
Senior Application Consultant
STS Center of Expertise
Agilent Technologies R&D and Marketing GmbH & Co.KG
Herrenberger Strasse 130
CCST-BUS
D-71034 Boeblingen
Germany
Phone: +49-7031/464-6493
Fax: +49-7031/464-4708
Email: jose_moreira@xxxxxxxxxxx
AS OF 6/1/2006, NEW E-MAIL ADDRESS: jose.moreira@xxxxxxxxxx
______________________________________________________
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
On Behalf Of esayre@xxxxxxxx
Sent: Dienstag, 30. Mai 2006 19:19
To: joel@xxxxxxxxxx
Cc: manickavelu_m@xxxxxxxxxxxx; istvan.novak@xxxxxxxxxxx; Ed Troy; =
si-list@xxxxxxxxxxxxx; weirsi@xxxxxxxxxx
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
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
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=20
> <etroy@xxxxxxxxxxxxxxx>, si-list@xxxxxxxxxxxxx
>=20
> This is similar to a question I posted about an Intel app note for an=20
> Ethernet controller that recommended a plane split between the=20
> controller andEthernet connector with built in magnetics. Intel also=20
> suggested that capsof various values might be needed to bridge across=20
> 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=20
> said the plane split was necessary toprevent common mode noise on the=20
> ground plane from coupling across the Ethernet magnetics which are=20
> designed to attenuate common mode noise. I also had a thought to=20
> eliminate ground planes around the Ethernet connector excepton the=20
> bottom layer of the board thinking there would be less coupling from=20
> 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=20
> intervals which are small compared to the wavelength of the noise on=20
> the planes. This is more commonly done with plane splits where the DC =
voltages of the planes are at different potentials.
> Joel
>=20
>=20
> steve weir wrote: Manix, no. There are many misconceptions out there=20
> about the myth of ground and its relation to noise isolation. Those=20
> myths get propagated into misguided applications of moats and such.=20
> 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]=20
> [mailto:si-list-bounce@xxxxxxxxxxxxx[2]] On Behalf Of=20
> istvan.novak@xxxxxxxxxxx[3] Sent: Friday, May 26, 2006 6:26 AM To: Ed=20
> Troy; si-list@xxxxxxxxxxxxx[4] Subject: [SI-LIST] Re: Question about=20
> split gnd planes Ed, Splitting more than one ground plane in the=20
> stackup requires a lotof consideration, and mostly it is not=20
> necessary. Isolating a sensitive circuit (e.g., analog input,=20
> low-jitter oscillator) may be a good idea, but instead of cutting a=20
> 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=20
> be isolated, or you can put the patch on a signal layer. Regards,=20
> 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]=20
> Question about split gnd planes If you have a circuit board that=20
> requires a split gnd plane over a small section of the board, and you=20
> have several ground planes, should only one have the split (the one=20
> nearest the side containing the components that require analog ground) =
> while the rest of the ground planes are continuous, or should the=20
> split section be on all ground layers? I would think that you should=20
> only have it on one layer. Also, if it should only be on one layer, I=20
> would imagine it would be best to connect it to the digital ground=20
> with one, and only one, via. Is that generally correct? What are some=20
> good references for layer stackups, etc? I know I saw one, once, but=20
> can't remember where. Ed
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