At 10:08 AM 10/15/99 -0500, you wrote:
>>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
>
>I'm using some of the old National LDOs (LM2941).  They can take the
>voltage, but the quiescent current is way more than 5ma!
>
>
>>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!
>
>Low voltage and current starved zeners suck.
>
>I've used series (REF-02) voltage references for precision low current
>regulators in the past.  You might look into replacing the zener with a
>micropower shunt regulator (bandgap ref) that will regulate much better at
>low currents (10 uA).
>
>Check out LM385 (shunt) and LM2936 (series).

Another one to look at are the MAX 666 series, and the pin equivalent but
better Analog devices 666 series.  Also for precision and low power, we use
the REF19x series.

Kelly

William K. Borsum, P.E. -- OEM Dataloggers and Instrumentation Systems
<borsum@dascor.com> & <www.dascor.com>San Diego, California, USA