What cap mfr. to use?

Toss a coin ?

I'd tend to trust Panasonic btw. They tend to have good specs but even they have various options. When purchasing for a new project, they are my first choice for prototyping. At the economy level I'd go for Samwha ( had excellent results ).

Graham

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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.

Eeyore wrote in news: snipped-for-privacy@hotmail.com:

Me too. I used them to replace the low ESR caps on an ITX mainboard that runs in fairly hot and enclosed conditions. The board failed previously because caps with dodgy electrolyte were used, it leaked, dried, causing poor power conditioning and early video failure. The problem has not reappeared with the Panasonic FM electrolytics I used.

Panasonic and Nichicon make about 20 different grades and "types" of electrolytics. Does one just look for high operating temp and low ESR, or are there other factors (or combinations thereof) to consider?

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

John

Manufacturer's data sheets are more comprehensive. And don't forget ripple current.

Graham

If you get their full catalogues, there should be a selection table.

Graham

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).

Dimensions (which affects life reduction due to self heating as well as simply fitting the available space), lifetime (at temperature), cost, availability, low operating temperature, maximum ripple current, leakage current, tolerance, working voltage, surge voltage, etc.

"William Sommerwerck" wrote in news:gtv62f$ea9$ snipped-for-privacy@news.motzarella.org:

Worked for me. :) I bet there is a more proper way to go, but I just assumed that those two considerations would give me the best lifetime, though I also add in a choice for a higher voltage cap because voltage headroom also certifies an easy ride and long life.

Spehro Pefhany wrote in news: snipped-for-privacy@4ax.com:

Those are interesting, but I found that it's often easier to focus on a subset. Dimensions are often dictated by the space, so I just go for higher voltage caps which will be bigger anyway, that solves the self-heating and the voltage overhead for safety.

Availaibility is interesting, but often the best parts get neglected till people cry over spilt unobtainium. Although they cost a bit more, it might be best to go for them anyway, that way suppliers will take care of availability. The best way to make unobtainium is the slow fission of amnesium...

One thing I never remember well is the correlation between ripple current and ESR, though I imagine low ESR types tolerate ripple currents better because they will dissipate less power per amp of ripple.

Maybe for replacement use, where someone else has already crunched the numbers.

I always try to use the most bog-standard, inexpensive, available and reliable parts. There's more than enough excitement to be had in the parts that really ought to be oddball.

I'm not eager to take dusty stock off the hands of distributors under most conditions.

Yes, all other things being equal. One thing that's not obvious unless you study the data is that self-heating, even when within the allowable ripple current rating, can dramatically reduce the lifetime of the capacitors (and often also the product).

Spehro Pefhany wrote in news: snipped-for-privacy@4ax.com:

That's true, though I sometimes analogise with the old batteries, SP2 and HP2, in the UK, they were the safe middle ground of zinc carbon types, with all kinds of esoterica lingering from portable valve radios and specialised photoflash types. SP was standard power, HP, high power. SP was cheaper. Both endured (even now, I think) because people realised it was often better to pay more for HP as you usually got better bang per buck that way. I sometimes think the electronics industry is like buyers who all go for SP because it's cheaper, and still middle ground, and who come to mourn the demise of HP and likely only have themselves to blame. :)

I think just edging a tier upward in performance is worth the cost. For one thing it is a good way to beat the disability culture that besets manufacturing now, and if unchecked, will result in government pressures to reduce inefficiency and waste. I suspect most makers would rather jump than be pushed, especially if jumping early gives them something to help advertise the product's reliability.

Nor me, but by then it's usually too late anyway. Dusty amnesium is about as appetising as sweaty gelignite.

Lostgallifreyan wrote in news:Xns9C04D85B06216zoodlewurdle@216.196.109.145:

Strange typo... meant 'disposability'

And also for completeness and no good reason whatsoever, I wanted to mention that bell boxes and bike lights were also a source of some very bizarre and esoteric 'standard' batteries best avoided, now seen in museums, probably..

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?

"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.

After the bad caps debacle one manufacturer, it might be Gigabyte, moved to the OSCON type in which case it may very well be true.

Graham

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.