The bus is differential and I don't see transformer coupling to it, so that means the interface to the bus is differential as well, right? I don't understand in that context what is meant by grounding, other than the shield(s).
Ken Javor Phone: (256) 650-5261 > From: Brian O'Connell <[email protected]> > Reply-To: Brian O'Connell <[email protected]> > Date: Tue, 12 Jun 2018 22:36:53 +0000 > To: <[email protected]> > Conversation: [PSES] Automotive EMC question > Subject: Re: [PSES] Automotive EMC question > > CAN bus assumes a 'standard' 120 ohm termination for the ends of each CANL/H > twisted pair. The ISO11898-x series talks about physical layer stuff, to > include splitting the termination with caps (but have had problems with that). > > LT or TI or ??? has some app notes on this subject. It emphasized that there > must be only one grounding path for the nodes on the bus. > > Brian > > > > From: John Woodgate [mailto:[email protected]] > Sent: Tuesday, June 12, 2018 2:53 PM > To: [email protected] > Subject: Re: [PSES] Automotive EMC question > > I hope it also at least recommends that the grounding is at the sending end, > so that the cable capacitance is charged from the low-impedance source. I > guess that, e.g. in the auto environment, the risk of large shield currents is > too great to allow routine grounding at both ends. But I suppose that > grounding via a capacitor at the receiving end is not banned. If possible, > this capacitor should be of the lowest possible inductance, which is not > difficult with SMD, and if several capacitors are disposed radially around the > end of the shield and grounded at their outer ends on a metal ring, the > grounding should be good up to at least 1 GHz. > John Woodgate OOO-Own Opinions Only > J M Woodgate and Associates www.woodjohn.uk > Rayleigh, Essex UK > On 2018-06-12 22:41, Ken Javor wrote: > The CAN bus spec says that shield(s) are to be grounded at one end only. How > does this work vs. meeting stringent rf RE and RS requirements at frequencies > where cables are electrically long? > > Thank you, > > Ken Javor > Phone: (256) 650-5261 > > - > ---------------------------------------------------------------- > 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 > <[email protected]> > > 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 <[email protected]> > Mike Cantwell <[email protected]> > > For policy questions, send mail to: > Jim Bacher: <[email protected]> > David Heald: <[email protected]> - ---------------------------------------------------------------- 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 <[email protected]> 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
