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
