[sdiy] electrolitics for pcb power input

[John Luciani]

On Dec 5, 2007 6:06 AM, Fernando de Izuzquiza <listas at fdi.jazztel.es> wrote:
>
> Hi,
>
> I may buy some electrolitics in large quantity to get them chaper and
> I'd like to know about the criteria to choose them.
>
> These will be used at the power input on each circuit board.
> I see some people use 10uF, some other 100uF.
> Some at 25V, others 35V or 50V.
> (I'll be using +-15V PSUs)
>
> Also, worth to get them of the Panasonic types? Long life is
> important for me.

For long life you need to run the capacitor at lower temperatures.
The specifications you want to look at are ESR, maximum operating
temperature and lifetime at the maximum operating temperature.
You get roughly a factor of 2x in lifetime for every 10DegC drop
in temperature.

This may be overkill for your application but take a look at the
Nichicon PW Series electrolytic capacitors. IIRC these are rated
at 5000 hours at 105DegC.

> And, wich other values are the most common for circuit usage (I know
> Harry preffers non-polars for that!)
> 4.7uF? 47uF?

For ceramic caps I would get 0.01uF, 0.1uF, 1uF, 4.7uF in an X7R dielectric.
For values 1000pF and lower I buy them as required and use NP0 dielectric.

(* jcl *)


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