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.
USB non-buspowered GND - what to do
Started by ●July 22, 2004
Reply by ●July 22, 20042004-07-22
Tobias Alte wrote:> 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
Reply by ●July 23, 20042004-07-23
Reinardt Behm wrote> > 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 >Thanks.
Reply by ●July 23, 20042004-07-23
"Tobias Alte" <tobias_alte@web.de> wrote in message news:cdp2t5$kq4$05$1@news.t-online.com...> 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.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.
Reply by ●July 25, 20042004-07-25
"Reinardt Behm" <reinhardt.behm@t-online.de> wrote in message news:v8apdc.732.ln@main.behm.eae.de...> Tobias Alte wrote: > > > 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 hasits> > own > > supply so I don't need the USB supply. > > > > Should I connect the USB bus GND to the GND at the board for EMVpurposes> > ( and leave USB +5V unconnected ) or must I connect none of the USBsupply> > 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. >You do? With differential signals?
Reply by ●July 25, 20042004-07-25
On Sun, 25 Jul 2004 11:07:18 GMT, "steven" <stevenPANTSvh@pandora.be> wrote:>"Reinardt Behm" <reinhardt.behm@t-online.de> wrote in message >news:v8apdc.732.ln@main.behm.eae.de... >> Tobias Alte wrote: >> >> > 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. >> > >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