On 27 October 2014 13:17, Neil wrote: > My power supply is fairly basic -- reverse protection diode, small > resistor, 8V regulator, then 5V regulator. 0.1uf caps on the input and > output of the regulators. Total current draw is 60mA. > IF you genuinely have no larger capacitors anywhere in the system then the holdup time for a full Vin dropout approximates zero quite well indeed - work it out. If you really have no electrolytics or similar anywhere on Vin then that's almost certainly enough reason to have a problem like this. then R --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .