I believe that your experts are wrong...4.2 is a rather odd number to come up with. The most common requirement here is SUPPLEMENTARY INSULATION for a PRIMARY CIRCUIT at 250Vrms (as defined by EN 60950) between the TIP/RING (line side, or TNV-3 side) and the modem or device side. 2.5mm of surface creepage and 2.0mm of air clearance is required here. This assumes that your modem or device side already has sufficient isolation from Mains, which is almost always the case.
Many countries in Europe require only BASIC INSULATION at a working voltage of 150VDC, which equates to a 1.6mm creepage spacing requirement. This also assumes that you have sufficient isolation from Mains to you modem. If you don't have sufficient isolation from Mains, your requirement will be 5.0mm. This would be consistent with the REINFORCED INSULATION requirement between Mains and the Tip/Ring side. It is possible that your consultants are correct for your particular case...however, it would be a very unusual case... They are correct about one thing...EN 60950 is the correct standard. feel free to call if you have any further questions, Mel Pedersen Midcom, Inc. Homologations Engineer Phone: (605) 882-8535 [email protected] Fax: (605) 882-8633 I disclaim anything that may be wrong. ---------- From: Diaco Davari[SMTP:[email protected]] Sent: Thursday, October 08, 1998 2:29 PM To: [email protected] Subject: Crepage/Clearance On Telecom Modem design Hello Folks, Does anyone know what the crepage distance shall be across the isolation from the line side to modem side within the DAA of Modems? Which document/standard refers to this specific spacing in detail ? I have been told by local experts on EN60950 that I need 4.2 mm spacing across the isolation. Apparently I do not need to have the spacing on the top of the board in alignment (or registration) with the spacing on the bottom of the board. Regards, Diaco --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators). --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
