On 10/08/06, Olin Lathrop wrote: > > Yes, but the resistor will drop 2.65V all the time when the load is 10mA, > even when the input voltage is the 5.0V it's supposed to be. That means > the > PIC Vdd will be 2.35V with 5V in. The 10F will operate down to 2V, so > maybe > that's OK, but the OP should at least be aware of this limitation. The output has to be around TTL level so even if 10F works in 2V the result might not be acceptable. If this is not acceptable, you could try a 5.6V zener with emitter follower > as a crude regulator. That requires one additional NPN transistor from > the > plain shunt regulator described above, but will only drop about 700mV when > the input voltage is below about 5.7V. Above that it will regulate > reasonably well to 5V up to the C-E voltage limit of the transistor. The > extra $.03 for the MMBT4401 or whatever will be worth it in many > applications. OK, thanks for the tip. By the way, 10mA is quite high for a 10F itself, although the whole circuit > could easily draw that. The OP needs to provide some real specs. The specs said the max is 80mA but I am not sure in what circumstances? Thanks again, Tamas -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist