>
> Byron, my man.  you are doing it the hard way.

I know. I know. But every time I start to look at inductors I get the willies.
Every time I read a switcher datasheet, it seems to come up with an inductor
component that's completely unavailable. The cross referencing you list
below isn't a cut and dried activity.

Also I'm trying to limit myself to stuff I can get in town here in Atlanta.
Fortunately we have one of the few RadioShack.com stores which carries
everything in their commercial catalog, including inductors. So I'm listening.


>
> The charge pump chips I have used are suited for low currents.  I know you are
> going to reinvent for more current, but why?  6+2.5 watts is not a place to
> start breaking ground on leading edge inductorless concepts.
>
> National simple switcher (and linear tech and others, for that matter) show an easy
> to build Buck-Boost that goes from +12 to -12 with a relatively easy cookbook
> circuit.  And even though a flyback would be a fabulous solution, yes, you need to
> have them wound for you ($$$).  The apps on the simple switchers show easy to get
> toroid inductors.  They list Schott, Pulse, and Renco.  I quickly crossed a 68uH 2A
> inductor to a Miller 5707 in Digikey.  It is oversize, but what the hell, you are
> only building one.  I see this app under LM2576, near the end.  It shows a 700mA
> output, +12 to -12 converter.  Build two of those, and you are in business!

I see. I read that data sheet. Every other example show's an input voltage
that's higher than the regulated voltage.

>
> Remember, when you build it and it has a massive amount of ripple, to go back to
> the app note and study their recommended current path connection diagram.
> Following layout practices like they say will take a horendously noisy switcher and
> make it very manageable.  The dead giveaway is when you ground the scope, then put
> the probe tip on the same ground point, and you get lots of nasty noise.  If so, it
> is time to take an asprin and warm up your iron.  Make the layout paths correct,
> and recheck.

I see that I can get the parts intown. Will take a crack at it.

BAJ