Jim, There is absolutely no reason why the 250V caps would be required between the connector shell and the PCB digital GND, and it is especially true since you are using UTP. I could foresee some trying to argue it in case of STP, which I do not support either, but I am not going there now. Lightning surge is of no concern here, because Ethernet is rated 1500Vrms (IEEE spec), and is guaranteed to hold any common mode surge up to 2121V pk. If you zap any Ethernet transformer with common mode surge up to that level, you will get very low-level transients through the transformer. Differential-moode surge test wold be different, as some folks who deal with GR1089 have learned, but that requirement is now gone away for Ethernet, with the latest revision of GR1089. If you zap a port above the isolation-level that is required/speciified, the cap is not going to help in any way, because the transformer that is in prallel to the cap may get punctured anyways - no guuarantee for anything above 2121V pk. Neven
-------------- Original message -------------- From: "Jim Eichner" <jim.eich...@xantrex.com> > We're being hit with a requirement that I don't understand. > > We are using a shielded Ethernet connector that contains the typical 2kV > cap from the common point of the 75 ohm resistors to the shield. This > is used on the output of an off-the-shelf Ethernet transceiver module, > and the mfr of that module is telling us we need to connect the > connector shield to their digital ground through a 1nF 250V Y-cap, not > directly. > > 1. Why not directly connect the shield to digital ground? > > 2. Why would a Y-cap be required? The cap would be joining two parts of > the same circuit, so it would not be across an isolation boundary. I > can't think of a reason to require either the 250V! rating or the Y > rating. > > Any thoughts anyone? > > Thanks, > > Jim Eichner, P.Eng. > Manager - Compliance Engineering > Xantrex Technology Inc. > e-mail: jim.eich...@xantrex.com > web: www.xantrex.com > > Confidentiality Notice: This email message, including any attachments, > is for the sole use of the intended recipient(s) and may contain > confidential and privileged information. Any unauthorized review, use, > disclosure or distribution is prohibited. If you are not the intended > recipient, please contact the sender by reply e-mail and destroy all > copies of the original message. > > - > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list. Website: http://www.ieee-pses.org/ > > To post a messag! e to th e list, send your e-mail to emc-p...@ieee.org > > Instructions: http://listserv.ieee.org/request/user-guide.html > > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > > Scott Douglas emcp...@ptcnh.net > Mike Cantwell mcantw...@ieee.org > > For policy questions, send mail to: > > Jim Bacher: j.bac...@ieee.org > David Heald: emc-p...@daveheald.com > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________ - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
