That's it, BUT! I need to start at a lower voltage, not to mention the
negative supply... The big capacitance would give a longer decay. What you
show, essentially is a LPF. Problem occur just before that, on the
switching part. Thus make also the 5Vcc part compromised by ripple due to
charging big capacitors via FET or something like that.

I'll try the modules you suggested, maybe LPFing them with PI filters on
input and LPF+PI on outputs.

Cheers!

Ale

On Wed, 3 Dec 2003, Rick C. wrote:

> The easiest way to achieve that purity is to use a series of resistors and
> capacitors, maybe two or three stages to isolate any possible ripple. You need
> not use large capacitors. They will not impede the ripple.
>
> -----r-----r-----> +
>            |        |
>            c       c
>            |        |
> ----------------->G
>            |        |
>            c       c
>            |        |
> -----r----r-------> -
>
> Rick
>
> Alessandro Queri wrote:
>
> > It seems you have not red all the message. I'm wondering if there's a way
> > of achieve that BELOW the 50KHz switching freq. The second part of the
> > question was: does anybody know the result of switching big capacitors at
> > lower frequencies? IE: Let's say I want to charge a huge capacitor once
> > and then drop with a linear regulator to the voltage I need. That would be
> > "clean", as there would be no ripple at all. Anyway, as the aim is to feed
> > a current loop circuit which is to be connected to a 12 bit ADC, the max
> > ripple would be 12v/4096=2mV or less. That would be "really clean", and
> > (grin) outstanding the medium 40mV ripple of many switching IC.
> >
> > Ale
> >
> > On Wed, 3 Dec 2003, Olin Lathrop wrote:
> >
> > > Alessandro Queri wrote:
> > > > I have 5v supply (single rail, DC) and I want REALLY CLEAN +/-12v @
> > > > 50mA. Consider that conversion should not generate noise in 50 KHz+
> > > > Band AT ALL!!!
> > >
> > > This is not possible.  It is a useless specification.  Figure out how much
> > > you can really tollerate.  And, how clean is "really clean"?
> > >
> > >
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