I don't think you can use this directly, but I ran hours of tests on a tantalum cap at full rated potential while applying large amplitude microsecond spikes with no hiccups, no heating until I got quite extreme. The cap was rated at 30 WVDC and I biased it at 28 Vdc, while applying all kinds of nasty spikes. The report accounts for at least seven hours of applied bias potential and spikes, with no failure until after several hours of a multi-kilovolt, 20 us long spike finally destroyed it.
The reference is: K. Javor, Investigation Into the Effects of Microsecond Power Line Transients on Line-Connected Capacitors, NASA/CR-2000-209906, NASA Marshall Space Flight Center, AL 35812, February 2000, pp. 33. and it can be found at: http://see.msfc.nasa.gov/see/ee/eepub.html ---------- >From: "Chris Maxwell" <chris.maxw...@nettest.com> >To: "EMC-PSTC Internet Forum" <emc-p...@majordomo.ieee.org> >Subject: Tantalum Capacitor Reliability >Date: Mon, Jul 29, 2002, 2:41 PM > > > Hi all, > > By the way, thank you to the various group members for the responses > regarding the hazardous atmosphere classifications. > > One of my colleagues is testing a new design. He has designed a buck-boost > switching converter which has tantalum output capacitors. We have looked > at his design and gone through the calculations. His output current is 4 A > maximum. His output voltage is 12 VDC His caclulated ripple current is > 800 mA. He needed a 120 mV ripple voltage, so he put 8 each of 68 uF, 20 V > tantalum capacitors (with 150 mOhm ESR) in parallel on the output. Each > cap is rated for approximately 800mA of ripple current. > > He has seen two failures of these capacitors during initial testing and > demonstrations. Meanwhile, many initial units run fine. From what I can > gather, he hasn't violated any design rules. He has 20V rated caps on a > 12V circuit. He has a ripple current rating of 8 X 800mA (8 caps in parallel). > > It is tempting to just increase the voltage rating to 25V or 35V....but > why? Even if he does, how do you prove that the problem is fixed. It > would take months of testing the new capacitors to get the history that we > have on the existing design. > > I guess what I'm looking for is some tantalum capacitor wisdom... Should > we just go ahead and use 25 V or 35V caps in this 12 V application? Are > tantalum caps that flaky? What is the possibility that we don't have a > design problem; but just a couple of bad capacitors? Is there some piece > of knowledge out there that would help us tell the difference? > > Chris Maxwell | Design Engineer - Optical Division > email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024 > > NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA > web www.nettest.com | tel +1 315 797 4449 | > > > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > http://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
