I'm designing a battery powered device, which must be turned on by an external 3.3V impulse from a comparator output (TLV3201), and for the sake of power efficiency I want the MCU to power itself off when it has finished processing the event. For the self-poweroff circuit I've found the following solution:
The P-channel MOSFET is powered off by default by pulling it's gate to VCC via R1, but when the EN pin is pulled high, either by the comparator (push-pull op-amp) output or the MCU (after it has got power), the P-channel switch is opened to supply power to the MCU.
The problem is that the high signal from the comparator may stay high for many seconds, even after the MCU has done it's work, and I want the MCU to be able to shutdown the power regardless of the comparator output (after it has initially enabled the switch) until the next time the comparator output rises. How could that be done?
- Added schematic of the comparator circuit.
- The power supply is an unregulated Li-Ion battery (~3.7V). The 3.3V regulator is to be placed after the P-channel switch as part of the Load.
The comparator is used to sense the resistance connected between IN1 and IN2, which may switch between ~1.5 kOhm and ~5.5 kOhm. 1.5 kOhm resistance results in a high level output of the comparator, and 5.5 kOhm is low level (0V) output.
Edit 2: The MCU will be a ESP-07 Wi-Fi module (ESP8266). I am currently researching its deep sleep capabilities and power consumption.