From: "Ian Buckner"
Subject: Re: maximum reverse voltage allowed on electrolytic caps?
Date: Thu, 14 Nov 2002 13:40:05 -0000
Organization: Agilent Technologies
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"Tom Bruhns" wrote in message
> "Frank Bemelman" wrote in message
> > I always assumed that, let's say, a few 100mV reverse voltage
> > doesn't matter, but is this a correct assumption ?
> I think that's OK for (most) aluminums, and a bit less for
> I'd be inclined to use a Schottky diode to limit the voltage, if
> was a chance it might try to go too high, especially on tantalums.
> That is, I'd limit it to _very_ few hundred mV.
> Interesting that others have noted aluminums that short just sitting
> there. That's not a very friendly behavior, and one I haven't
> personally noticed. We do have a policy of significantly derating
> aluminums, especially, and tantalums too. Running at half rated
> voltage, max, is strongly encouraged. The derating is biased by the
> amount of ripple current the capacitor will see in the particular
> design, and by the ambient temperature.
Well, I used to think that tantalums were OK for small reverse bias
Looking at the AVX datasheet on their TAJ parts at:
www.avx.com/docs/Catalogs/taj.pdf on page 10 it says:
"Continuous application of reverse voltage without normal
polarization will result in a degradation of leakage current.
In conditions under which continuous application of a reverse
voltage could occur two similar capacitors should be used in
a back-to-back configuration with the negative terminations
Once upon a time Philips used to do some aluminium parts
that were actually specified for (low) reverse voltage operating.
"Solid aluminium electrolytic" as I recall, since discontinued.
They were intended to compete with the bead tantalums, but
were more expensive.