I agree with Lee's suggested method and have done so in the past with no
issues.
Christian
On Wed, May 9, 2018 at 12:12 PM, <leeritchey@xxxxxxxxxxxxx> wrote:
There is no electrical reason why you need to connect these two. If you
do
connect them, do it in only one place and do it with a DC connection. I
make that connection on the side of the PCB where the unshielded wires exit
as a way to minimize potential EMI escaping on those unshielded wires.
Don't know where all of the rules of thumb come from about capacitors and
multiple connections.
Lee RItchey
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx <si-list-bounce@xxxxxxxxxxxxx> On
Behalf
Of Joel Brown
Sent: Wednesday, May 9, 2018 9:47 AM
To: gurushankara@xxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Logic ground and chassis/safety ground
Unless you have a requirement or other reason to keep them isolated It
would
be best to connect them together.
If you decide to keep them them isolated then add multiple capacitors
between signal and chassis ground at each chassis connection point that can
be populated with different value capacitors or zero ohm resistors. Another
option is to have a chassis ground plane layer in your PCB that is
connected
to signal ground at multiple points with capacitors. If you don't have a
solid RF connection between signal and chassis ground then there can be an
RF potential between the two grounds that can radiate if you have antenna
structures such as slots in your enclosure or external cables.
Joel
On Wed, May 9, 2018 at 9:16 AM, Guru Shankara <gurushankara@xxxxxxxxxxx>
wrote:
Hi Experts,chassis.
I am working on a modem design that is powered by an AC/DC supply
(isolated).
The design includes a base board that hosts a mezzanine/daughter card
and both the baseboard and the mezzanine cards are powered by 12V DC.
The chassis walls and misc. mechanical hardware have a conductive
coating on the inside and will be connected to the
chassis/safety/earth ground of the AC/DC power supply.
As the name implies, the chassis/safety/earth ground provides for
safety of the operator if there is a situation where the higher
voltage side line of the AC/DC supply rips off and makes contact with the
So, I prefer NOT to connect the board logic ground to the
chassis/safety/earth ground of the supply.
Any thoughts on if I should connect them together or not?
Also, if they need to be connected, is there a recommended method?
Really appreciate your help.
Thank you,
Gurushankar
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