I sometimes use a resistor in series with the input for the same effect,
costs a bit less and also no heatsink. Often you can get away with not
using a heatsink at all if you use a low dropout reg.
George

----- Original Message -----
From: "Russell McMahon" <apptech@PARADISE.NET.NZ>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Saturday, May 15, 2004 3:53 PM
Subject: Re: [EE:] Cascading Regulators


> > Since you mention cascading, I have this situation frequently and
instead
> of
> adding a (relatively) large heatsink, I use 2 regulators in
"series" -- a
> 7810 to drop the 13.8V to 10V, then send that to the 7805 to drop it
to 5V.
> Cost is another 35c or so for the 7810 regulator.
> >
>
> A word of warning - while there may be some advantage in doing this,
there
> is no free lunch.
>
> This practice reduces the dissipation in any one component but the
overall
> dissipation is the same.
> If the regulators are on the same heatsink, the heatsink has to
dissipate as
> much energy as it would have had to if there had only been one
regulator.
>
>
>         Russell McMahon
>
> --
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