Hi all,
Due to the way a circuit is switched on or off, I would like to have a small capacitor hold a processor on for about 50mS after detecting that the power was turned off so that I can store some data. The circuit voltage is about 4.4V, and if I use a Schottky isolation diode, then the capacitor charged voltage would be about 4.1V or so. If I allow around 20mA current, and use a 2.2mF capacitor, I should get about 200mS before the cap voltage drops below the microprocessor reset level of about 2.7V.
If this seems feasible, what sort of resistor should I use to limit the charge current at switch on. I don't know what is appropriate.
I would imagine the processor would have to track a minimum switch on time before it would attempt to save the data.
cheers
Tony