Jim, I have used a similar technique to get good high-frequency performance from an ethernet shield without the effects of dc and low frequency loops. The capacitor ratings are likely based on the maximum voltage that may be impressed on the shield.
Scott B. Lacey On 7 Mar 2007 at 12:05, Jim Eichner wrote: > 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: [email protected] > 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 message to the list, send your e-mail to [email protected] > > 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 [email protected] > Mike Cantwell [email protected] > > For policy questions, send mail to: > > Jim Bacher: [email protected] > David Heald: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieeecommunities.org/emc-pstc > - 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 [email protected] 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 [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] 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 ______________________________________________________________________
