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Grounding Chassis of USB Powered Device to USB Ground/ Shield?
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Par3689:
I am working on a project which is a USB powered device. Data lines and the power line of the USB are isolated from the main circuitry.

I am using an anodized aluminium enclosure for the board. I am not sure what to do with the chassis/ enclosure.


* Should I keep the enclosure floating ie. without connecting to any ground
* Or should I connect it to USB ground/ shield
What is the standard way of doing this properly?

More info: I am using hammond chassis similar to this one 1455N1201
soldar:
Unles there is a good reason not to do it I would connect the enclosure to the USB shield.
Par3689:
And should the shield be directly connected to USB ground? Right now I am connecting USB shield to USB ground with RC parallel combo

If a charged individual touches the chassis,

* should 1M resistor to ground be used, like the ESD strap?
* or there should be low impedance path from chassis to shield to USB ground
Is there any other scenario I have to take care of? I have put TVS diode for the data lines and Vbus.

I am not able to decide on this  :-//
coppercone2:
search the forum, people literally fight about putting some kind of impedance between the shield and the cable (it gets pretty ridiculous).

i would only put impedance on the shield if something was severe garbage and i was forced to do it. imo it means something is fucked up.
Par3689:
While searching on the forum I found this post by free_electron https://www.eevblog.com/forum/projects/usb-device-circuit-design/msg235913/#msg235913

He says to connect RC combination from system ground to system shield with R = 4.7k and C=27pF

For my device will this be sufficient?

I am attaching his reference image




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