Better use a 5.1 volt zener to be safe; the 5.5 may not actually protect until a good bit above 5.5.
----- Original Message ----- To: "Multiple recipients of list CHIPDIR-L" <[EMAIL PROTECTED]> Sent: Tuesday, February 11, 2003 12:49 PM > Hi Jens, > So what I may want to do is put a 5.5V Zener across the power input and > also have something like a polyfuse in the power line to handle when the > zener shorts. I guess this needs to be a fairly hefty zener (a wall-wort > could supply up to a couple amps unregulated easily) to withstand the > current before the ployfuse kicks in. An suggestions on power rating? > Thanks, > > At 09:14 AM 2/11/03 -0800, Jens Sch�nfeld wrote: > >At 07:59 11.02.2003 -0800, you wrote: > >>Hi, > >>I have a question about protecting a circuit from an overvoltage > >>condition. We > >>have a new device that we are planning to use a regulated 5V wall-wart type > >>device for power. They have also requested overvoltage protection in case > >>someone plugs in a 6V or 8V unregulated supply by accident. My expertise > >>is mostly digital so I am not sure what the best and cheapest way to do this > >>would be. Thanks in advance for any help or pointers. > > > >Most 5V digital semiconductors can take 5.5V without taking damage. Just > >put on a 5.5V Zener diode, and let the fuse on the power supply do the > >rest - if there is one. You may have to add it to your circuit if you're > >not sure. The Zener diode perfectly fits into the circuit that filters the > >digital "pollution" out of the power lines, add it somewhere on the 5V > >side. If you have a current-compensated coil, I'd put it _before_ that > >(PSU side!), because those coils are usually rated only slightly above the > >current that your circuit needs. > >ciao, > >-- > >Jens Sch�nfeld > >(from Germany, a little paranoid about CE as you may have guessed :-)) > > -Bob > -------------------------------------------------------------------- > Robert Ritchey > Quest Engineering & Development > 1328 East Cottonwood Lane > Phoenix, AZ 85048-4765 > Tel: (480) 460-2652 > FAX: (480) 460-2653 > E-Mail: [EMAIL PROTECTED] > E-Mail: [EMAIL PROTECTED] > E-Mail: [EMAIL PROTECTED] > E-Mail: [EMAIL PROTECTED] > WWW: www.QuestEngDev.com/ > WWW: www.Smart-Fly.com/ > -------------------------------------------------------------------- > > -- > Author: Robert Ritchey > INET: [EMAIL PROTECTED] > > Fat City Network Services -- 858-538-5051 http://www.fatcity.com > San Diego, California -- Mailing list and web hosting services > --------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message > to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in > the message BODY, include a line containing: UNSUB CHIPDIR-L > (or the name of mailing list you want to be removed from). You may > also send the HELP command for other information (like subscribing). > -- Author: Syd Levine \(AnaLog\) INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
