CJT wrote:

Ross Herbert wrote:

On Wed, 16 Jun 2004 02:51:34 GMT, CJT wrote:

|Jim Yanik wrote:
|
| "Jerry G." wrote in
| : | | |You should use the
ones that are rated for 105 deg Cels. Use any good
|quality cap, as long as the specs are proper. Just make sure that the
|voltage rating is the same or higher than the original. A higher
|voltage rated cap will most likely last longer, as long as the heat
|and stress to the cap is within its tolerance. It is heat that
|destroys the caps more than anything else.
|
| | | I beg to differ.
| In switchers you not only want 105deg caps,you want LOW-ESR
caps.IMO,the | low ESR is more important.That's where the stress
comes from.
| |
|I don't see ESR specified on catalog pages for capacitors (e.g. at
|Digikey), so what should I be looking for in the specifications, and
|what is a good value, in your opinion?


No, but they often state "low impedance" and "long life" along with
the temperature rating and often quote impedance values. For instance
look at this page http://dkc3.digikey.com/PDF/T042/SectE.pdf


Well, that URL points to a pdf that's 145 pages long, so I'm still a
little unclear just what you're looking at.

OK, I've done some Googling and reading since I posted that, so I now
understand better the significance of tan delta. However, it seems to
me, looking at the Digikey catalog, that the available 105 degree
capacitors are fairly competitive in that spec, so I'm not sure it's
really all that useful as a selection criterion.

I'd appreciate your insights.



You will see that they have a column actually showing the impedance at
100KHz as well as the rated ripple current. These factors are vital
for a person wishing to select a capacitor for a specific function.
Looking at this Panasonic type I can guess that it would be ideal for
the intended application of the OP. There are undoubtedly even higher
spec devices in the Digikey catalog but I'll leave that to the OP to
chase up.





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