Your device will generate radiation (unintentional) from the circuit boards.
If you don't connect logic ground to the case, the energy will be coupled to
the case via parasitic capacitance.
If you do connect the logic ground to the case, both the case and the logic
ground will be (roughly) at the same potential.
If any cables exit the chassis it will be important to connect the grounds.
As others have noted, there may be safety requirements for connection (or
isolation) depending on the applicable standards.
Curt
________________________________
From: si-list-bounce@xxxxxxxxxxxxx <si-list-bounce@xxxxxxxxxxxxx> on behalf of
Guru Shankara <gurushankara@xxxxxxxxxxx>
Sent: Wednesday, May 9, 2018 11:16:34 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Logic ground and chassis/safety ground
Hi Experts,
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 chassis.
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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