You will find a lot of good, proven information about shield grounding for balanced interconnects in the Journal of the Audio Engineering Society Volume 43 Number 6 1995 June. Don't be put off by the 'audio'; the techniques are valid up to 100 MHz or even higher. Put simply, the cable shield should be regarded as a pipe connecting two water tanks. So connect so that it doesn't leak! Furthermore, connect the shell to the outside of a conducting enclosure, because connecting to the inside turns the cable shield into a transmitting antenna potentially filling the enclosure with VHF/UHF fog. Now the question changes to 'how to connect a conducting enclosure to the circuit ground?' Unless the enclosure isn't conducting, of course, In that case, connect the shell-shield-shell chain to circuit ground at the sending end, so that the cable capacitance is charged from a low-impedance source. But that is a very brief summary. The paper by Neil Muncy explains all that and more, and it all works. With best wishes DESIGN IT IN! OOO - Own Opinions Only <http://www.jmwa.demon.co.uk/> www.jmwa.demon.co.uk J M Woodgate and Associates Rayleigh England Sylvae in aeternum manent. From: Grasso, Charles [mailto:charles.gra...@dish.com] Sent: 22 June 2017 17:52 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] USB dongle connector shield filtered grounding Greetings And just when you thought it was safe to go back in the water..!! Q: Has this august forum heard of/seen/used a filter combo technique to tie the connector shield to the circuit ground successfully? ######### ILLUMINATION ############# ############### My question has to do with USB dongles and the connection of the cable shield to circuit ground. I am running across a lot of posts recommending NOT having a low impedance connection from the shield to the circuit ground at the dongle connector : rather the shield is kept separate (at least AC wise) from the circuit ground using a ferrite/cap or resistor/cap combo. I have also read that the industry convention now is to tie the shield ground and the circuit ground at the host only and "float" the peripheral connector using the filter combo previously stated. I have not used this EMI suppression technique but I find it simultaneously intriguing and counter intuitive. Q: Has this august forum heard of/seen/used this technique successfully? TL/DR: Found new USB grounding technique, am suspicious of it, asking for the forums help. TIA ***************** ************** *************
Summary of techniques can be found here: [https://forum.allaboutcircuits.com/threads/usb-device-cable-shield-connecti on-grounding-it-or-not.58811/] - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org <mailto:emc-p...@ieee.org> > All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) <http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org <mailto:sdoug...@ieee.org> > Mike Cantwell <mcantw...@ieee.org <mailto:mcantw...@ieee.org> > For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org <mailto:j.bac...@ieee.org> > David Heald <dhe...@gmail.com <mailto:dhe...@gmail.com> > - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
