[SI-LIST] Question on ESD/EMC optimized GND Layout on PCB
- From: Hermann Ruckerbauer <hermann.ruckerbauer@xxxxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Wed, 18 May 2011 09:01:00 +0200
Hello all,
I'm searching for some information on optimized GND/shield
implementation on the PCB for optimized ESD/EMC behavior and I hope that
some of you could share a bit of your experience.
Lets think about a PCB with an IO panel e. g. for Graphics and USB
interfaces. The chassis is connected to the receptacles and these are
connected to a Copper layer called "Chassis GND" on the PCB. The PCB
itself does have a GND plane for referencing and current return for high
speed signaling called "Digital GND".
I have seen some designs that e. g. do connect the "digital GND" of the
PCB directly to the Shielding/Chassis GND of the IO Connectors of a PC
system board.
But in some design guides I have seen some different implementation an
optimized ESD/EMC Layout:
Split "digital GND" of the PCB and the "Chassis GND" (GND connected to
IO Panel and chassis) by a minimum distance and if possible make this
"chassis GND" surrounding the hole PCB. Connect the "chassis GND" by a
single connection to "Digital GND" and add AC coupling capacitors
between Chassis and Digital GND. Connect this shield GND as good a
possible to Chassis (e.g. by mounting holes).
Maybe you have another opinion, or have any more detailed feedback on it.
Questions would e. g:
- Where should the connection between Shield GND plane of the IO Panel
and digital GND plane should be made ? (As far as possible away from the
IO Panel where the ESD event migth occur ?)
- Should this connection be a trace on PCB (how wide ?), or e. g. via
Resistor or even ferrite bead?
- How wide the gap between the Chassis GND plane and Digital GND plane
really needs to be ?
- Is there any special requirement on the capacitors coupling Digital
and Chassis GND (e. g. on ESD behavior).
Thanks for any direct feedback and maybe some links for further reading ...
thanks and regards
Hermann
EKH - EyeKnowHow
Hermann Ruckerbauer
www.EyeKnowHow.de
Hermann.Ruckerbauer@xxxxxxxxxxxxx
Veilchenstrasse 1
94554 Moos
Tel.: +49 (0)9938 / 902 083
Mobile: +49 (0)176 / 787 787 77
Fax: +49 (0)3212 / 121 9008
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