Thanks everyone for sharing his knowledge. I will try to summarize your feedback and let me know if you have anything to add. For a given telecom system required chassis connections are: - battery +48V in NA and possible signal ground (digital 0V) - battery +48V, 0VR at the system and signal ground in EU although 0VR connection to the ground is not wanted in NA. No comment on pros and cons apparently both work within a proper environment.
Dorin Marko Radojicic wrote: > Hi Joe, > > Those are the ever-present questions, aren't they? > > ESD is fairly easy to answer: Protect all the apertures especially LEDs. > Proper EMI gasketting will also deal with ESD as it provides a low-impedance > path to CG/FG. Remember that the skin depth phenomena of high-frequency > currents will keep the majority of the ESD power on the surface of the > system (if the EMI gasketting is good). > > As for Lightning surge, that needs special care to design a system that > dumps the energy back to the faceplate or bulkhead and not onto your PCB. I > use a moat structure and multi-point bond the "surge ground" to the > faceplate. The moat provides a reference plane for the intended signals. > Some intuitive good design practices are to make the moat as long and narrow > as possible, use only a single moat, use fast-acting surge suppressors such > as sidactors, etc. > > Cheers, > Marko > > -----Original Message----- > From: Joe Finlayson [mailto:[email protected]] > Sent: Tuesday, September 10, 2002 12:02 PM > To: 'Marko Radojicic'; 'John Juhasz'; 'Dorin' > Cc: 'EMC-PSTC - forum' > Subject: RE: Grounding architectures for COs > > Hi Marko, > > I'm curious what measures you and others take to protect against > ESD, Lightning, etc when implementing a multi-point bonding scheme of signal > ground to frame/chassis ground. I can definitely see the advantages for > EMI. > > Thx, > > Joe > > -----Original Message----- > From: Marko Radojicic [mailto:[email protected]] > Sent: Tuesday, September 10, 2002 2:22 PM > To: 'Joe Finlayson'; 'John Juhasz'; 'Dorin' > Cc: 'EMC-PSTC - forum' > Subject: Grounding architectures for COs > > Greetings, > > Bonding of the different system grounds is, surprisingly, a very involved > topic. > > Historically, CO equipment in North America (NA) has been Star-IBN (Isolated > Bonding Network) sometimes referred to as ISG (Isolated Signal Ground). (I > won't go into all the reasons behind it.) > > In Europe (EU), a Mesh-IBN, sometimes referred to as Common Bonding Network > (CBN), is used. > > Battery Return is also problematic. In NA, it *must* be held isolated from > CG/FG. In the EU, it *must* be bonded to the CG/FG! > > Both can be effectively deployed but the EU version is more robust to > violations. > > In terms of pros and cons, multi-point bonding the signal ground (SG) and > chassis ground (CG) is, by far, the most effective architecture for EMC > applications as it offers EMI currents a lower impedance path back to the > source. For all my high-speed, high-power designs, we've implemented this > multi-point SG to CG architecture. > > The downside to this strategy is that you can no longer be Star-IBN > *compliant* however you will be Star-IBN *compatible*. NA ILECs (Verizon > included) have been accepting this grounding architecture for over a decade > now so there is no new ground that you'll have to turn over. > > Hopefully this explanation has cleared up the situation a little. For > further reading, I'd recommend ITU (formerly CCITT) K.27 (the granddaddy of > grounding documents - Figure 1 is invaluable) as well as ETS 300 253 > (Earthing and Bonding for Telecom). > > Cheers, > Marko > > -----Original Message----- > From: Joe Finlayson [mailto:[email protected]] > Sent: Tuesday, September 10, 2002 9:03 AM > To: 'John Juhasz'; 'Dorin' > Cc: 'EMC-PSTC - forum' > Subject: RE: Inrush and EN61000-3-3 > > John & Dorin, > > Please clarify as I am not aware of a requirement to isolate Signal > Ground from Frame Ground. Please reference GR-1089-CORE, Section 9.6.2 as > well. > > Thx, > > Joe > > -----Original Message----- > From: John Juhasz [mailto:[email protected]] > Sent: Tuesday, September 10, 2002 11:12 AM > To: 'Dorin' > Cc: 'EMC-PSTC - forum' > Subject: RE: Inrush and EN61000-3-3 > > Be careful Dorin. For Central Offices, they need to be isolated. > > John A. Juhasz > > GE Interlogix > Fiber Options Div. > Bohemia, NY > > -----Original Message----- > From: Dorin [mailto:[email protected]] > Sent: Tuesday, September 10, 2002 9:12 AM > Cc: 'EMC-PSTC - forum' > Subject: Re: Inrush and EN61000-3-3 > > Hi, > > I am looking for a comparison, pros and cons, on the signal ground > connected versus not connected to the chassis in a telecom system. Any > help is appreciated. > > Thanks, > Dorin > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: [email protected] > Dave Heald: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > http://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: [email protected] > Dave Heald: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > http://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: [email protected] > Dave Heald: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > http://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
