I have designed a power delay switch which is intended to cause a short delay while a reservoir capacitor fills up before giving power to my microcontroller due it needing a short burst of high current before settling down to it's operating current of around 5uA.
The power delay circuit (see below) itself works fine and gives me the delay I need and everything powers up as it should, however my issue arises when the circuit loses power.
The circuit gets 2V from a regulator which regulates batteries (3V) down to the 2V I want to power the MCU as this will ensure that the supply voltage is constant which makes ADC readings and calculations easier to calculate.
Now the problem that I am having is that when the batteries are disconnected (circuit loses power) the two capacitors (C1 and C2) take a long long time to discharge (about 3 minutes) - this isn't a problem is power is reestablished quickly (under 2-3 seconds) which is how long it takes the voltage to drop below the MCU's minimum supply voltage, after this point, however, the MCU completely shuts off and won't power back on unless the capacitors fully discharge (<100mV) and then the power can be applied again and it will work as it should. So I feel I need a way of completely draining the capacitors in the event of power being lost. It might be worth noting that the capacitors initially discharge fairly quickly down to about 0.6/0.7V before beginning the painfully slow discharge process - if anyone has any bright ideas as to how to resolve this, that would be great.
Another alternative is to possibly design a slightly better delay switch that will cut the power line from the MCU when power is lost - as you might notice this one will not do that, but again I can't think of any ideas for that as current consumption is a big thing and this current design draw virtually no current once running properly.