[SI-LIST] Re: EMC
- From: Chris Landrum x311 <clandrum@xxxxxxxxx>
- To: "'chris.mcgrath@xxxxxxxx'" <chris.mcgrath@xxxxxxxx>
- Date: Wed, 5 Nov 2003 09:16:17 -0500
Ground filling is useful to create inner layer capacitance for the power
sub-system of the PCB. By filling GND on a signal layer that is directly
adjacent to a PWR plane a capacitor will be created. This capacitor is
often times MUCH more effective at providing energy to components because it
is far less inductive than a normal leaded or chip capacitor.
EMI can be caused by an improperly designed power sub-system. What can
happen here is current gradients can be formed in the PWR/GND planes that
can effectively cause radiation assuming there is an antenna nearby. Also
of concern is VCC and GND bounce. The plane capacitors formed can help
avoid this problem.
By ensuring that the chips are getting the proper energy such that VCC and
GND bounce do not occur, you are thereby reducing the probability that EMI
problems can be caused by the power sub-system.
-----Original Message-----
From: Chris McGrath [mailto:chris.mcgrath@xxxxxxxx]
Sent: Wednesday, November 05, 2003 8:35 AM
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: EMC
The "ground filling" is a topic that has been discussed at my company
recently and I wanted to get the list's feedback on why this is done.
We never do ground filling on any layers and the only reason that I have
ever heard for it was to reduce EMI, but given the disadvantages
(increased thermal profile, potential for crosstalk, PCB viewer and
gerber viewer complications, etc.) and the fact that I have never been
able to find data or any science to back up the EMI argument, I don't
see any benefit to ground filling on signal layers. (Of note is that by
using the term "ground filling", I am not referring to "thieving" to
equalize the copper distribution to facilitate PCB fabrication.)
I am very interested in hearing feedback from any of you.
-Chris
> -----Original Message-----
> From: Suresh.K [mailto:sureshk@xxxxxxxxxxxxxx]=20
> Sent: Wednesday, November 05, 2003 2:54 AM
> To: subramani
> Cc: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: EMC
>=20
>=20
>=20
> Dear Sir,
>=20
> According to your Board Stack you have two strip lines and=20
> one assymmetrical dual stripline,but the two strip lines are=20
> bounded by one side power plane and Ground Plane on the other=20
> side......
>=20
> If you have both side ground plane reference for the strip=20
> lines ,you can route all the Impedance controlled signals on=20
> Layer2 & layer8,because strip lines bounded by ground planes=20
> will be best layer for better signal=20
> integrity.
>=20
> But now you have assymmetrical dual stripline bounded by=20
> ground planes,so I beleive that layer 5&6 may be better=20
> option for routing clock signals,which will useful for return=20
> path, but you need to care of tandem=20
> pair of traces.
>=20
> and regarding board power plane EMI,you can follow 20H rule=20
> on layer2& layer9 power planes to reduce the power plane EMI=20
> and Top & Bottom layers you are doing Ground fill, so I think=20
> the device EMI will be controlled by the Ground fills.
>=20
> Regards,
> Suresh.K,
> Vth EDA Lab,
> C-DOT,
> Bangalore-52.
>=20
>=20
>=20
>=20
>=20
> On Wed, 5 Nov 2003, subramani wrote:
>=20
> > Hello,
> >=20
> > I am doing a board design. It has to pass stringent EMI tests.
> >=20
> > Mine is a 10 layer board.
> >=20
> > The board stack up is
> > 1 TOP component, GND filling
> > 2 Power
> > 3 signal
> > 4 GND filling
> > 5 signal
> > 6 Signal
> > 7 GND filling
> > 8 Signal
> > 9 Power
> > 10 Bottom Component, GND filling
> >=20
> > The board has SDRAM operating at 100Mhz. Where should I route the=20
> > clocks. Could anyone tell me about the ways and means of=20
> reducing EMI.=20
> > The SDRAM is placed that is near to the edge of PCB. Will it cause=20
> > radiation. Is there a formula for keepout distance.
> >=20
> > Regards
> > Subramani
> > Mistral
> >=20
> >=20
> > ------------------------------------------------------------------
> > To unsubscribe from si-list:
> > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the=20
> Subject field
> >=20
> > or to administer your membership from a web page, go to:=20
> > //www.freelists.org/webpage/si-list
> >=20
> > For help:
> > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> >=20
> > 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
> >=20
> >=20
>=20
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>=20
> or to administer your membership from a web page, go to:=20
> //www.freelists.org/webpage/si-list
>=20
> For help:
>=20
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>=20
> 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=20
> Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
> =20
>=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 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
------------------------------------------------------------------
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:
