Hi Aubrey,
That is certainly true. I have found in my work that multiple signal returns to
chassis connections is both lower cost and quickest to market. But, of course
there are always significant exceptions to any rule and I do whatever is need
to meet requirements if cost or time to market.
I often put âhooksâ into designs to anticipate problems and workarounds
that do not require a relaying. For instance, including one, sometimes more,
optional connections to the chassis using 4 resistors at 90 degrees (to
minimize coupling between resistors to insure lowest inductance) around a PCB
mounting hole. I leave the pads shorted but can unshort them with a knife in
the lab if needed to damp PCB resonance. If needed the shorts are deleted from
the layout and resistors used, typically four 100 Ohm resistors, but the value
can vary depending on measurements and calculations (no simulation needed here,
a very simple hand calculation).
Doug Smith Sent from my iPhone IPhone: 408-858-4528 Office: 702-570-6108 Email:
doug@xxxxxxxxxx Website: http://dsmith.org
On Mon, May 14, 2018 at 12:45, Aubrey Sparkman
<asparky@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:
Doug,
The lowest cost solution is not always the best solution when âTime to
Marketâ is a significant factor. Sometimes the quickest to Market solution is
the best as long as it meets specs.
Aubrey
Sent from my iPhone
On May 12, 2018, at 10:15 PM, Doug Smith <doug@xxxxxxxxxx> wrote:
Again the lowest cost solution is best and often shielding is the most
expensive solution! A Faraday cage should not be necessary for a good design.
Doug
University of Oxford
Department for Continuing Education
Oxford, Oxfordshire, United Kingdom
--------------------------------------------------
Doug Smith
P.O. Box 60941
Boulder City, NV 89006-0941
TEL/FAX: 702-570-6108/570-6013
Mobile: 408-858-4528
Email: doug@xxxxxxxxxx
Web: http://www.dsmith.org
--------------------------------------------------
On Sat, 12 May 2018 09:24:51 -0700, wrote:
The massive shielding is what we call a good Faraday Cage. Best solution if a
product allows it.
-----Original Message-----
From: Grasso, Charles
Sent: Friday, May 11, 2018 7:12 AM
To: doug@xxxxxxxxxx; leeritchey@xxxxxxxxxxxxx
Cc: joel@xxxxxxxxxx; gurushankara@xxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: RE: [SI-LIST] Re: Logic ground and chassis/safety ground
Sun Microsystems (many yrs ago now) adopted a DO160 /MILSTD approach to noise
abatement for their high end graphics products . That is: *no*
interconnection(between logic and chassis) technique combined with massive
product shielding and were very successful doing that. By successful I mean
that Sun passed all of its EMI/Immunity specs
with flying colors. Costly - but back then margins were not an issue!!
Thanks
Charles Grasso
(w) 303-706-5467
