At 08:34 1998-02-06 -0500, you wrote:
>I have a battery power PIC application that I have the opportunity to
reduce the
> power by running
>the PIC at 3V. I looked at Linear Technology, Maxim, National
Semiconductor and
> Harris for a LDO
>micropower 3V regulator and found MAX663 666 and 689. I was hoping for a
three
> terminal TO-92
>type part. The circuit has 4 Alkaline cells (6V) and draws 1.4ma @6V at 3V
the
> draw is 0.74mA and
>runs continuously until the batteries need replacement.
>
>I don't  any experience using  switching regulators for battery power. Is
this a
> viable option or is a
>linear regulator a better choice for battery life.
>
>Any  favorites??
>
>- -Mark

Zetex (and others?) have a 3V or 3,3 V in 3-pin, poth TO92 or compatible
and also in SMT. But you don«t need the expensive low drop types if you
have 5V from battery.

But now as you want to exactly half the voltage, is seem stupid to burn off
half of the battery power, plus power consumption of the regualtor. 

Small inductive switchers are expensive and have significant internal
cuonsumption.

Instead, use a charge pump, and your batteries will not last twice as long
(as with linear regulator, but four times! (output is half input voltage
and double input current)

The Harris ICL7660 and clones are by datasheet defined as voltage doubler
or inverter. They also with careful design work great as a voltage
halver/current doubler. Own consumption is almost nothing, and noise low.

However I use to design own cap pumps for two reasons. 1) The above chips
are relatively expensive. 2) I sometimes don«t need as much power as they
deliver, and sometimes I use much more.
/Morgan
/  Morgan Olsson, MORGANS REGLERTEKNIK, SE-277 35 KIVIK, Sweden \
\  mrt@iname.com, ph: +46 (0)414 70741; fax +46 (0)414 70331    /