On Tue, Mar 30, 2010 at 2:50 PM, MSR7 wrote: > > I have to admit i didn't completely understand how to read all the datash= eet > informations. > > Now i've tried to use the 1N5346 (Silicon 5 Watt Zener Diodes) > > The datasheet shows: > Steady-State Power: 5 watts at TL < 25=B0C or 1.47 watts at TA =3D 25=BAC > > TL =3D Lead temperature at 3/8 " (9.5mm) from body > TA =3D ambient temperature on FR4 PC Board > > Thus actually I have a 1,47W Zener diode and not a 5W? > It's still heat, i think it is due the 115mA flowing through it. The Izt = of > this zener is 150mA. As long as you are passing 115 mA though a 9.1V zener, you'll be dissipating about a watt. The zener power rating and case size doesn't affect the dissipation. Your job as a designer is to remove the energy before the temperature rises too much. Moving the heat around is easier with large packages, but you will still need to think about where you want to put the heat. Probably using a heat sink of some kind to get the heat into the ambient air / ambient circuit. Regards, Mark markrages@gmail -- = Mark Rages, Engineer Midwest Telecine LLC markrages@midwesttelecine.com -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist