The second arrangement, with the normal power supply on full power, the supercap charging through a resistor and powering the PIC through a diode, is in fact required to keep the supercap from drawing inordinate power-up surges. The only drawback is your PIC has to be powered for at least 30 second s(or whatevewr the RC timeout is) to ensure that the supercap is able to ride through. I have seen this arrangement on commercial products. -- Lawrence Lile Senior Project Engineer Toastmaster, Inc. Division of Salton, Inc. 573-446-5661 voice 573-446-5676 fax Jinx Sent by: pic microcontroller discussion list 02/09/2004 04:19 PM Please respond to pic microcontroller discussion list To: PICLIST@MITVMA.MIT.EDU cc: Subject: Re: [EE:] Post battery pull runtime Can you adapt either of these ? (drawings from memory - just saved many folders to CD and haven't documented them yet to make finding actual diagrams easy) -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body