Re: gEDA-user: Switching regulator question

[Bob Paddock <bob.paddock@xxxxxxxxx>]

On Sunday 17 June 2007 20:53, Dan McMahill wrote:

> Or better yet, use ... For tantalums in 
> switchers, it used to be the case that you should derate the voltage by 
> 2x since you can get uneven voltage drops in the dielectric under 
> transient conditions. 

Tantalums should also be "Surged Rated", if used at the input
of switcher, to keep them from exploding when you turn
the unit on.

>  The actual capacitance was basically a secondary 
> consideration.  I just hoped the bean counters never tried to find a 
> cheaper "replacement part".

I've had the Been Counters do exactly that.  I designed the output
caps based on ESR.  Generally if you have a low enough ESR,
you will have enough output capacitance.  Been Counter
looked at the capacitance value and voltage and said
"we'll use this, they are half the cost", alas they were twice
the ESR.  Then by some Dilbert Logic it was my fault
when the design started to fail in the field.


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