[SI-LIST] Split Ground Planes
- From: "rakesh" <rakesh@xxxxxxxxxxxxx>
- Date: Thu, 28 Oct 2004 11:05:49 +0530
Hi All,
While appreciating what Guru Doug has mentioned,
I have a doubt. Would the Split in the Analog and Digital ground below a
ADC qualify as a split plane
Best Regards
Rakesh
> > [Original Message]
> > From: Doug Smith <doug@xxxxxxxxxx>
> > To: <jose_moreira@xxxxxxxxxxx>
> > Cc: <si-list@xxxxxxxxxxxxx>
> > Date: 10/26/2004 3:04:16 PM
> > Subject: [SI-LIST] Re: Split Ground Planes
> >
> > Hi Jose and the group,
> >
> > I normally reply personally to people to avoid the glut of
> > "out-of-office" messages, but feel I needed to add to this discussion.
> >
> > Signal propagation is an important but small part of the trouble you
> > can get into with split planes if not implemented properly. Even if
> > you manage to get the signal propagation right, system reliability can
> > be severely compromised as it is easy to turn every cable in the
> > system into a great receiving array to pick up impulses you can easily
> > miss in the lab, but your customers won't!
> >
> > I worry also about the common mode voltage that can result across the
> > board and drive enclosures, cables, etc. This voltage will cause
> > radiation that depends on a lot more that the board itself. Also
> > common mode voltages can be developed from outside sources as
> > mentioned above.
> >
> > There are probably thousands of modes to get in trouble with split
> > planes of which the referenced paper covers a subset. You can cover
> > many of the problems by not ever allowing a trace to cross the slit.
> > Even DC signals like LEDs are generally too noisy to allow to cross a
> > slit in many cases.
> >
> > Most of the examples of splitting up ground planes I have seen were
> > not necessary and just caused problems (remember that at high
> > frequencies everything is connected together whether you want them to
> > be or not, lots of articles on my website about this effect). There
> > are a few justified cases though. Video can be one example where the
> > signal can be degraded by just a small amount of powerline current
> > (hum bars in the video).
> >
> > In general, I would not recommend splitting planes unless you can
> > state and MEASURE (to confirm) why a split plane is needed.
> >
> > Doug
> >
> > jose_moreira@xxxxxxxxxxx wrote:
> >
> > > Nikhil,
> > >
> > > you can find the article on the IEEE xplore site (if you have acess)
or
> =
> > > in a library.
> > >
> > > Details:
> > >
> > > Signal propagation and radiation of single and differential microstrip
=
> > > traces over split image planes
> > > Orhanovic, N.; Raghuram, R.; Matsui, N.;
> > > Electromagnetic Compatibility, 2000. IEEE International Symposium on
=
> > > ,Volume: 1 , 21-25 Aug. 2000=20
> > > Pages:339 - 343 vol.1
> > >
> > > Best Regards
> > > Jose
> > >
> > >
> > > -----Original Message-----
> > > From: Nikhil Patel [mailto:npatel@xxxxxxxxxxxxxxxxxxx]
> > > Sent: Dienstag, 26. Oktober 2004 15:40
> > > To: si-list@xxxxxxxxxxxxx
> > > Subject: [SI-LIST] Split Ground Planes
> > >
> > > Hi all,
> > > I have been doing a lot of reading on Split ground planes and am a bit
> > > confused now. Do most people use just one solid ground in the
schematic
> > > and
> > > layout for EMI issues or do you prefer split ground planes? Any input
is
> > > greatly appreciated.=20
> > >
> > > Thanks
> > >
> > > Nikhil=20
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