Chris, I think a nearly perfect "plug it in and go" solution for your stated problem (gotta cover my bases ;-)) is the Nat Semi LM2936 regulator. This offers - 40 volt maximum input 15uA worst case quiescent current for 100uA load (9uA typical) Rising to 200/500uA at 10mA load. I have found that the actual quiescent current seems to be better than this. Dropout voltage is 5.5 volts Standard pinout. Std 3 pin TO92 or 8 pin SO pkg The only real limitation of these compared to "normal" regulators is the 50mA max Iout, which probably won't be a problem in your application. Somewhat dearer than 78L05 but may not be an issue in your application. I use the 5 volt version but I believe a 3v version MAY be available. Lets see, for 1 volt drop in 7 seconds on 220uF current drain is about I = 220/E6 x 1/7 ~= 30uA. This means you will get 1 volt of droop over 7 seconds for every 30uA of load current.or so. This is rough but indicative. As you seem to have 30 volts in I guess you can droop from 30v to say 6 volts = 24 volts so load could be 30uA * 24 ~= 750uA. Should be ample for a lowish powered PIC circuit. Are there more details which make this not work? regards, Russell McMahon _____________________________ >From another world - www.easttimor.com What can one man* do? Help the hungry at no cost to yourself! at http://www.thehungersite.com/ (* - or woman, child or internet enabled intelligent entity :-)) -----Original Message----- From: Chris Eddy To: PICLIST@MITVMA.MIT.EDU Date: Saturday, 16 October 1999 03:30 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. >