In a message dated 12-1-2003, Dan Roman writes: > It won't pass the UL (or CSA) overvoltage testing. You need > the 600V part for that. Hi Alex:
I agree with Dan. It is possible to pass the UL overvoltage tests with two TS250 devices (one in tip and the other in ring), but a more typical application is to use one TS600 device. When considering the use of a PTC, it is important to keep in mind what your goals are. The main benefit of PTC devices is that they help in passing the M1 overvolatge test. Aside from this one advantage, they have some drawbacks in terms of size, series resistance, and lightning immunity. An alternative approach that typically has better lightning immunity is to use an appropriate telecom fuse such as the Teccor F1250T (several vendors make comparable parts that are specifically designed for telecom applications). The suitability of the fuse approach depends partly on the characteristics of the circuit being protected, so I can't make any blanket statements about one approach being preferred over the other. However, my preference has been to use a fuse unless other considerations force me to use a PTC. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) [email protected] http://www.randolph-telecom.com This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ieee-pses.org/ 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://www.ieeecommunities.org/emc-pstc
