> Any suggestions?
>
> I need to build up a PIC power supply with the following requirements.
>
> 12 volts DC in - fixed (not a battery)
> 7 to 10 volts DC variable output @ approx. 1 amp
> 5 volts fixed @ 200 mA
>
> Was thinking about LDO types of regulators, and would like the regulators to
> be efficient enough not require a heat sink.
>
> Can anyone recommend their favorite part number(s)?
>
> Also, would it be better to run the 5 volt regulator off the variable 7 to
> 10 volt regulator, or from the 12 volts?
>
> Thanks !!  ( sorry if this is a little off topic? )
>
> David
>

My particular favourite is the DC-DC switching step down converter
MAX649. Its output can be variable, its very efficient at 90%,
components run cool, typ 2 Amp output and the inductor is small and
off the shelf!
 The 5volt 200mA can be  a MAX639, needs no external
mosfet. Sure they are switching regs but at 300kHz its not that hard
to clean up even for sensitive ADC use.
Efficiency is not effected much by Vin (must be 4<Vin<16.5)
Check it out a www.maxim-ic.com

Note... there is an obsession with LDO regs these days but their use
is very limited, the low drop out is suitable for battery operation
where the power source is stable and the emphasis is low current
operation, low quiesent current and squeezing every last usable
volt out of the battery. The trade off is.. the ripple rejection on
an LDO sucks. It still wastes Vin-Vout x I as heat.

If you need an LDO then I recommend a MAX883.

Lance
Lance Allen
Uni of Auckland
New Zealand