Hi Ken and the group,
Even with low speed signals, they may have to tolerate tens of Volts or
more of fast glitches if the system is exposed to ESD. Sometimes slow
signals can respond to fast transients, and this would be a problem
crossing a plane break wiith such a signal.
Doug
University of Oxford
Department for Continuing Education
Oxford, Oxfordshire, United Kingdom
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P.O. Box 60941
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TEL/FAX: 702-570-6108/570-6013
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On Tue, 17 Jan 2017 16:32:25 -0700, Ken Wyatt <ken@xxxxxxxxxxxxxxxx> wrote:
Argh, my apologies Istvan. I indeed misread your description, as
pointed out by two of our colleagues, Vinu and Bert.
Yes, I agree that there are cases where planes may be split for
various reasons - mainly isolation, etc. We just need to be sure not
to cross that split with clock or other high-speed traces.
Crawling back into the woodwork… :-)
Cheers, Ken
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On Jan 17, 2017, at 1:05 PM, Ken Wyatt <ken@xxxxxxxxxxxxxxxx> wrote:- especially in very dense designs. You mentioned some cases where
Hi Istvan,I would have to agree there can be many trade-offs in board designs
splits were OK and I’d be interested in any additional specific
conditions where splitting the return (or reference) plane is OK from
a SI or EMI point of view, or can even make it better, as you point
out. > > In general, my experience has been in cases where high speed
(>100 kHz, say) clocks or other digital signals cross a gap in the
return plane, common mode harmonic currents are produced, which can
create not only crosstalk to victim traces, but worse, these currents
can flow out the outside of I/O cable shields, creating the potential
for radiated emissions. I understand there are situations where this
can’t be helped and I do believe there are cases where this
doesn’t matter much.
https://youtu.be/L44lTnQgv-oI created a short video demonstration of this effect.
questions related to EMC or EMI troubleshooting - at no obligation.Cheers, Ken
_______________________
I'm here to help you succeed! Feel free to call or email with any
I'm always happy to help!
<http://www.emc-seminars.com/> | Blog <http://design-4-emc.com/>Kenneth WyattWyatt Technical Services LLC
56 Aspen Dr.
Woodland Park, CO 80863
Phone: (719) 310-5418
Email Me! <mailto:ken@xxxxxxxxxxxxxxxx> | Web Site
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Connect with me on LinkedIn <http://www.linkedin.com/in/kennethwyatt><istvan.novak@xxxxxxxxxxx> wrote:
On Jan 16, 2017, at 9:05 PM, Istvan Novak
still would >> not use extreme phrases, like on page 6 you sayLee,
Nice article and I agree with most of what you say, though I
"Splitting a ground >> plane destroys its integrity as an ultralow
impedance connection between >> all of the components in a circuit
and should never be done." I agree >> that the reference (ground)
plane is very important and we should make >> sure it can serve its
purpose properly. However, in complex and high >> density designs
there are several conflicting requirements and sometimes >> making
careful splits on the ground planes are not only OK, it will make >>
the product outright better. There are occasions, for instance, when
we >> need to equalize and optimize the DC drop on planes and in
addition to >> optimizing the placement of components, we can also
help by splitting >> the planes, power and/or reference planes. If
signal traces are >> naturally routed alongside the split without the
need to cross it, the >> signaling will be OK. There are real,
working products with split >> ground planes.
With MartinRegards,A few weeks ago we had a prolonged exchange on what ground is.
Istvan Novak
Oracle
On 1/16/2017 6:53 PM, Lee Ritchey wrote:
expanded section onRowe, we did an article that appeared on the UBM site with this URL.
http://ubm.io/2ikEDat
I wrote another article that includes this as well as an
article isEMI and ground and Faraday Cages and how they contain EMI. That
the firstnow posted on the Speeding Edge web site, www.speedingedge.com
<http://www.speedingedge.com> for any who want to go beyond what
confusion around this topic.article covered.
Hope both of these help clear up some of the
------------------------------------------------------------------Speeding EdgeSee you all at DesignCon in Santa Clara at the end of the month.
By the way, I am planting flowers in my ground this month!
Lee Ritchey
P.O. Box 2194
Glen Ellen, CA
95442
707-568-3983
To get mad and wrote some blues.I just used the energy it takes
Count Basie
Worry is like a rocking chair,Or:
It keeps you busy but.
It doesn't get you anywhere.
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