Hi,

maybe I will say bullshit. But I think two things:

1. Use XTAL instead or RC
2. Use PIC with built-in brown-out detector or apply an external one. If
the voltage on the PIC drops, the cap approaches the empty state so it is
safer turn the whole device off at this moment. This is done by BOD.

I hope this helps.

Imre


On Fri, 15 Oct 1999, Chris Eddy wrote:

> 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.
>
>