Electronics > Beginners
Why are specific types of capacitors called for in terms of buffering an LDO?
jnz:
--- Quote from: T3sl4co1l on October 22, 2018, 06:31:38 pm ---
--- Quote from: jnz on October 22, 2018, 05:24:49 pm ---How can you be sure a 25V cap will hold up to automotive transients?
--- End quote ---
'Cuz I've done it. :-//
And there's all those times people have plugged 120V equipment into 240V mains, and the caps get hot but they don't bulge or vent for quite some time. I've even heard of e.g. 200V capacitors being reformed to operate at 350V or more (not that they'll necessarily meet any of their specs after such treatment).
Electrolytics are kind of like vacuum tubes: old, reliable (heh, well, "reliably unreliable" would perhaps be a better way to put it), able to take abuse for seconds, minutes even at a time. Just don't make a habit of it, and the overall lifetime won't be seriously impacted.
If you need design assurance -- no, I don't think you're going to find that in a datasheet or appnote anywhere, and the safe thing is to follow the datasheet as far as possible, and get manufacturer approval where the datasheet comes up lacking.
Hmm, on that note, this at least hints at it;
https://cn.tdk-electronics.tdk.com/download/540988/5f33d2619fa73419e2a4af562122e90c/pdf-generaltechnicalinformation.pdf
but the graph isn't to scale so I wouldn't draw any conclusions from it in regards to surge or transient rating. They do say they can provide transient ratings as needed, which may be a custom part request, so if you need a million pieces... Never hurts to ask if they have standard parts carrying such a rating, though.
Tim
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Ok, that's fine, and it's what I figured. There is a lot of experience that isn't in datasheets. I figure that part of the reason electrolytic are bad at high frequency stuff is probably why they seem to be fairly good at resisting transients.
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