Muhammad, during the common-mode surge, if your integrated connector is rated for 1500V min. isolation, you should not sink any CM surge current into your EUT (other than that due to any stray capacitance within the connector on the edges of the surge) - thus no dumping of surge current to your ground plane. The surge protection behind the connector would be for DM protection.
Regarding the requirement (R4-11) - it states that the "EUT shall not be damaged and shall continue to operate properly after the application..." Since this states *after* instead of *during*, my interpretation is that during the surge event, errors can occur (e.g. dropped bits, etc.), but after the surge, it must continue proper operation. My initial thought is that a reboot would not be acceptable, however, I suppose the acceptance of a non-manual-intervention reboot as a result if the surge event would depend on the definition of *after* (how long after would be acceptable?? should it be interpreted as *immediately after*?). Any other thoughts out there? -Scott Muhammad Sagarwala wrote: > Thanks Scott,The main reason I don't want anything getting into the > secondary side is, I don't want the common mode voltage on the ground > plane to rise once the surge protection cricuitry kicks in. This > could cause wierd problems on the board (e.g. chips might reset). I > don't clearly understand the requirement (needless to say I haven't > gone through the document in detail) if the equipment is supposed to > keep working after the surge or it is allowed to reboot and come on > line automatically.As always, inputs/suggestions/criticism most > welcome...Thanks a lot to all the people in this forum who responded > to my email. Your suggestions have/will help me a lot.Muhammad > > -----Original Message----- > From: Scott Lemon [mailto:[email protected]] > Sent: Tuesday, July 23, 2002 6:56 AM > To: Muhammad Sagarwala > Cc: [email protected] > Subject: Re: NEBS compliance for 100baseT / 1000base T > > Hello Muhammad, > > Unless you are customer premises equipment, you should only > have to meet the intrabuilding surge requirements of GR-1089 > (typically metallic ethernet interfaces are not intended as > outside plant lines). Using the RJ-45 with integrated > magnetics should be an acceptable configuration as long as > you are comfortable that the internal wiring can handle the > differential mode surge current (verify from supplier). > Most of them advertise at least 1500V isolation, so they > should not have a problem with the common mode surge. Why > are you concerned about placing the surge protection behind > the transformer? In differential mode, the integrated > transformer (1:1?) and magnetics should attenuate the > maximum amplitude transferred to the secondary side somewhat > and the surge protection can handle any that happens to make > it into the secondary, thereby protecting your chip. I know > Semtech makes a device especially for 100BaseT, but not sure > about 1000BT. > > Muhammad Sagarwala wrote: > > > Hello Gurus, > > > > I am new to this list so pardon me if my questions sound > > naive. > > > > The question I had was, for nebs compliance we need to > > pass power cross and lightening tests. For boards with > > copper ports (100baseT and 100base T), is it possible to > > use rj45 connectors with integrated magnetics and still > > get pass these tests. Has anybody done that - if yes, is > > it possible to share the method. I believe there are > > components (e.g. sedactors) one can use, but > > > > those are capacitve and might impact the signal > > integrity. Also, mostly that kind of stuff is used on the > > line side of the transformer. I am just a little bit > > hesistant to put in on the secondary side... > > > > Any input would be highly appreciated... > > > > Thanks > > > > Muhammad > > > -- > Regards, > > Scott Lemon > CASPIAN NETWORKS > RTP, NC > Ph:(919) 547-1078 > Fx: (919) 547-1010 > [email protected] > www.caspiannetworks.com > >
