John Honeycutt wrote:
> Gentleman, > I have designed an ADSL modem for my company. This modem will be sold all > over the world. In designing for EMI compliance, I have added a series > ferrite inductor in each Tip and Ring lead with two series connected > 220pf/3KV capacitors from each Tip and Ring lead to a midpoint which can be > optionally connected to chassis ground. > It is unclear to me if connecting the midpoint of the series connected > capacitors to the ground etch which connects to the PCB mounting bracket, > which ultimately is attached to the computer chassis, violates safety in > certain countries, i.e. Norway. > I would appreciate your comments. > John Honeycutt > Senior Hardware Engineer Hi, Refer to EN60950 or UL1950, Tip and Ring of your ADSL modem are classified as TNV3 circuit and it is required that BASIC INSULATION is provided (ie. 1.5KV isolation between Tip and Ring to your low voltage side SELV). You have 3KV capacitors from each Tip and Ring lead to the midpoint which will be connected to the GND etch, then chassis. I think it is OK as long as your PCB routing providing enough creepage and clearance as specified in these standards. Bye, -- Aaron Bui R&D Engineer SCITEC LTD Tel : + 61 2 9428 9914 Fax : + 61 2 9428 9933 Email : [email protected] http://www.scitec.com.au (For general Web posting: my views are just that and not that of my employer)
