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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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