Currently I am in the design process of circuitry for my energy harvesting circuit. I am using the CC1110F32 MCU from TI. I am using the Development kit boards that they created for this project.
The goal of this design is to have the MCU powered primarily by an energy harvesting unit we created. This module uses an LTC3108 energy harvesting chip coupled with a CP85 peltier module. The peltier module is being used as a Thermo-Electric Generator and we expect to receive .37 mV per 1 delta T (in degrees F).
What I need help figuring out is a way to have the MCU primarily powered by this energy harvesting circuitry, but in the event that the energy harvesting unit cannot support the power/voltage required by this MCU, the batteries (a set of two AAA alkaline) will power the system as a secondary method. Once the TEG's super-cap/direct voltage output has achieved that level again, the batteries will no longer be drained and the energy harvesting unit will once again be powering the MCU.
I am currently considering using some basic hard wired logic with MOSFETS/Diodes, but I don't want to have to use an I/O pin from the MCU to drive a MOSFET to change the location of the power. (If necessary I could, the system is quite low power) Also, I don't want the possibility of a MCU shutdown when the energy harvesting unit cannot supply the correct voltage.
If anyone has any thoughts, I thank you for your time and your collaboration.