I was just following the spec sheet for the $160 A/D chip I figure if they feel they can charge $160 for a chip they know a bit more about stuff than little old me lol. All the rest of my power supply caps were electrolytic or ceramic. -----Original Message----- From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Russell McMahon Sent: Sunday, April 25, 2004 1:13 AM To: PICLIST@MITVMA.MIT.EDU Subject: Re: [EE:] Power Supplies > we had a proto board that halfway through building developed a short, part > had to be out that day of course. After 3 people looked at it for half an > hour we were still no closer to finding it. Wound up pulling the valuablle > chips and connecting a 12V SLA battery across 5V and gnd, found the fault, a > tantalum cap and failed Electronics lessons to learn the hard way. 103. ***NEVER*** use tantalum capacitors in other than low energy high impedance circuits if the voltage may exceed the capacitors rating for any period of time. Here the word "any" assumes the normal meaning. eg a 1 uS pulse is included in the period "any of the time". A power supply rail is never a low energy high impedance circuit. 104. *** NEVER *** listen to people trying to assure you that rule 103 is bunkum. 105 Tantalum capacitors belong to the common class of electronic components which contain crisis detectors. These allow them to detect when the worst possible time to fail will be and to act accordingly. __________________ Tantalum capacitors are great fun. I have seen one, in sequence: - smell terrible - emit smoke - emit a jet of flame - shriek loudly - explode - short the power supply rail. Solid aluminium capacitors (NOT common Al electrolytics) are much more boring. Apart from having about the same capacitance for size as Tantalum caps, they lack all the interesting features. YMMV but only in terms of what combination and sequence of events will happen to you. RM -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body