In message <23107235.238391288251455817.JavaMail.www@wsfrf1230>, dated Thu, 28 Oct 2010, [email protected] writes:
> Basically, after going >through the routing recommendations, it is most of the time recommended >to >have the PHY close to the magnetics close to the RJ45 connector. The >closer the better. That's right. >I went though the si-list about this subject and I found some advice >like >the transformer should be close to the phy but the CM choke should be >close to the connector. The idea of having an EMI protection device >close >to the connector seems to make sense but I do not understand the reason >why the transformer should be close to the PHY : what is the advantage >versus having both the magnetics and the CM choke near the connector >and >therefore a "long" distance between the PHY and the magnetics ? Aren't you assuming that a 'long' distance was implied? If you look at the advice as: "the transformer should be close to the phy AND the CM choke should be close to the connector." ... it doesn't say that the transformer and choke shouldn't be close together. >Although having the CM choke near the connector seems to make sense I >have >also read about the fact that it it was ok to have quite a distance >between the transformer/choke and the connector but no mention there >about >some restrictions concerning the PHY to transformer distance. It's normally best to keep ALL distances in the PHY to connector chain as short as possible, to minimise any emission from the board itself and any possible disturbance of the impedance balance of the differential mode circuit by strays. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK If at first you don't succeed, delegate. But I support unbloated email http://www.asciiribbon.org/ - ---------------------------------------------------------------- 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.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
