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"low ESR" is not good enough for a purchasing spec. By the standards of just a few decades ago, all of today's electrolytics are low ESR. But whether anything meets your requirement is driven by the requirement, not bullet points in the capacitor maker's glossies.

It's easy to find electrolytics of same voltage and capacitance which have ESR specs different by a factor of 10 or more. It shouldn't be too surprising that package and size have a lot to do with ESR. If your requirements are not met by any commercially available capacitors, you might think about making your design more realistic :-).

Digikey etc. let you sort by ESR.

It is also possible to choose capacitors which are too low in ESR and lead to instability with low-dropout regulators or other circuits.

Tim.

And a lot of, maybe most, switchers are stabilized by the filter cap esr.

John

How critically are you trying to match the values?

Please remember that 'lytics are manufactured and sold with a rather wide tolerance range. For example, the Panasonic FM and FC series have a +/- 20% tolerance specification, and the nominal values they list (in the Digi-Key catalog at least) are around 20-30% apart... so there's some amount of overlap between the values you'd expect to get.

Older caps were often sold with -20% +80% tolerance, which meant that you could end up getting quite a lot more capacitance than you had "paid for".

In most cases, these days, I'd just look at the space I have available to fit the cap, and then pick the "equal or next largest capacitance, equal or higher working voltage" to what the BOM calls for. Unless there was a particular need for a specific value (e.g. for timing purpose) I wouldn't sweat about things like "the BOM calls for a 220 uF, and all they have in that size is a 330 uF."

And, if there were timing issues involved, I don't think I'd be using a 'lytic at all in that application!

I've heard good things about Nichicon, and have used them in some repair/retrofit projects. Don't have anywhere near enough information about long-term performance to be of help with your question, though.

For what it's worth, I've seen several of the PC-motherboard manufacturers touting their use of solid-electrolyte capacitors for the CPU VRM... and this is a high-current, high-ripple, low-ESR- is-very-important application. One manufacturer was citing a "50,000 hour" lifetime figure on the motherboard carton (although I think this assumes very good cooling of the board).

--
Dave Platt                                    AE6EO
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Speaking as someone who spent the last 10 years of his career as a senior engineer in a department repairing broadcast equipment, we found B C components (formerly Philips, formerly Mullard) to be among the most reliable and some we used to get from Farnell/Newark, with a sort of diamond design on them (I think possibly manufactured by multicomp), as the worst.

In article , Dave Platt writes

Are you sure there isn't a microdot in the small print with the words "electrolytic capacitors excepted" printed on it?

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"lifetime" is a word of dubious interpretation. Does it mean that it won't break in that time, that it can be repaired in that time if it does break, or something else?

If they claimed an MTBF of 50,000 hours, that would be different.

Sylvia.

AFAIUI, MTBF typically applies only to the flat part at the bottom of teh bathtub curve. They conveniently hack off the infantile failures at the left and the increasing failures as the useful life expires on the right. IOW, a product can have a much higher MTFB than the time it takes to wear out.

Also, 50,000 hours 24/7 is only 5.7 years, which is more-or-less what you'd expect out of a motherboard.

In article , Spehro Pefhany writes

Not from electrolytic caps, which was kind of the point. Even Panasonic specify only 10k hours for their top of the range electros.

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I guess that would be a rather serious problem if the temperature inside your computer case averaged 105°C = 221°F.

In article , Spehro Pefhany writes

Seen a modern mainboard recently? Voltage regulation MOSFETs with heatsinks on, some with their own extractor fans? Heat coupled to the capacitors by a few millimetres of thick copper PCB trace for excellent heat conduction?

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But isn't that at "high" temperatures, or some other extreme operating condition?

Certainly.

Have you put a thermocouple on the capacitors?

Shit, I'd generally be happy with 2000 hours MTBF.

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    W
  . | ,. w ,   "Some people are alive only because
   \\|/  \\|/     it is illegal to kill them."    Perna condita delenda est
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Less than 12 weeks? You have a bright potential future with Samsung, HP etc.

On May 7, 6:53=A0am, DaveC wrote: > Today I ordered electrolytic caps. It was frustrating. I had planned to get > the best low-ESR replacements for all the caps in some switching power > supplies. I discovered how limited any one manufacturer's low-ESR catalog is. > Many of what I needed (none of which seem to me to be esoteric values) were > not available. A couple of times I had to leave a particular manufacturer's > catalog altogether to find a value. >

I buy the replacement parts at a Hollywood dub house. Last year I bought 14.000 'lytics , 10,000 installed by 3 of us. My first choice in Panasonic FM but the selection isn't as wide as the second choice of FC caps. If I run into a physical size problem Nichicon PW series often helps. For surface mount first choice is Panasonic FK and sometimes HC series. If you're doing this a lot like we are, Metcal soldering irons are HIGHLY recommended. The STTC-126 tip (700 F 30 degree bent tip) is really good for clearing stubborn holes - usually ground planes with lousy thermal reliefs. A lifted pad is a very rare event with a good soldering iron.

100uf 25V (most common value for us) cost 20 cents in 1's 10.28 / 100 but are only $57.54 / 1000. I try for 1000s whenever possible.

G=B2

Stretch my old ring out.

I Am Kirk Johnson. "Anal Stretching, Wrenching & Expanding Specialist"