How to Build a Hysteresis Comparator Circuit for 5V On, 3.6V Off Supercap Control?

Hi, I am new to this forum and am more than a bit rusty in my designing (haven't since school years ago). I am running a microcontroller off of solar powered supercaps and what to not allow the circuit to turn on tell the caps have reached a threshold of 5V, but do not want them to turn off tell the caps drop below 3.6V. Is there a simple circuit to accomplish this? I know its easy to make a comparative circuit to work between 3.6 and 5, but I need it to not turn on tell 5 and not to turn off tell 3.6, a little more challenging.Any help would be great. (Current is not an issue as the actual regulators are turned on with a opticoupler, wanting to activate that opti with this circuit.)

What microcontroller are you using, many have a programable comparator or two on board which may be configured to drive a port pin. You may have to use a resistive voltage divider on the comparator input depending on the microcontrollers  supply voltage.Cheers,Richard

This comparator circuit controls the power circuit for the micro, it is 100% powered down tell 5V is present in the super caps.

Assuming that I have interpreted your information correctly, one way would be to use a pair of comparators and a latch. The latch would hold the state between the two transistions reqirred. The 5V threshold would turn the latch on, and it would remain on until the 3.6V threshold is reached. You would also have to take care that no glitches can upset the latch state during the power up phase, along with making sure that the latch is held in its approprite state. RC timing on the comparators and latch would probably take care of that, but watch out for slow changes on the latch power up reset, it would need to be Schmitt triggered.  There will be other ways to do it, but that's the first that comes to mind.Cheers, Richard.

Thanks Richard, that is exactly what I came up with after my initial post. It is good to get confirmation of my idea though. 

Take any 5V supervisory chip and use it to trigger a buck boost regulator. Something like an LT ADM181x-5, a simple 3 terminal device. When the cap hits ~5V it will power up the system and run it with a stable 5V until it can't and then it will shut down. That is a buck / boost regulator like say LTC3532.