Hi,
I'm currently working on a selfpowered USB device and have just a quick question. Maybe I overlooked/missed some info on the datasheets etc. but I am questioning myself what to do with the GND coming from the USB host. My device has its own supply so I don't need the USB supply.
Should I connect the USB bus GND to the GND at the board for EMV purposes ( and leave USB +5V unconnected ) or must I connect none of the USB supply pins with the device if I use a external supply ?
Thx for advice.
Of course you must connect the GND. At least you need it as a potentail reference for the USB signals.
-- Reinhardt Behm, Nauheim, Germany, reinhardt.behm@t-online.de
Reinardt Behm wrote
Thanks.
If you are new to electrical engineering, I'd suggest reading up on Kirchoff's Current Law and Kirchoff's Voltage Law.
If you are NOT new to electrical engineering, I'd suggest reading up on Kirchoff's Current Law and Kirchoff's Voltage Law.
:-)
--Keith Brafford Embedded Excellence, Inc.
its
purposes
supply
You do? With differential signals?
Yes, in practice you do. Unless one gavanicaly isolate one side, one need to keep the grounds of the different systems with 30V (On RS-485 anyway). I am not sure what the common mode range for USB is.
Regards Anton Erasmus
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