The LM2936 from National Semiconductor is exactly what you need.

40V max in 5V@50mA out  0.2V dropout 9uA quiescent  $1.22 US.

Craig

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Chris Eddy
> Sent: October 15, 1999 8:30 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Low current power for a PIC
>
>
> Associates;
>
> I have a PIC that must live off of a 220uF cap for 7 seconds.  I can get
> the PIC to consume low power, but I am having trouble getting the
> regulator designed.  The 78L05 sucks 2-3mA Q current, way too much.
> Looking for 50-100uA.  The low dropout regs are neat, but they have a
> very limitted Vin max.  I need 30V.  I built a pass regulator with a
> res, zener, and NPN trans, which meets my goals, but since the current
> through the zener is low, then as the V on the C drops off, then the V
> on the zener drops off, and the V on the PIC droops as well.  This
> causes the RC osc to skew, and my highly important timer gives me
> predictable garbage!
>
> Any great ideas?
>
> Chris Eddy
> Pioneer Microsystems, Inc.