I want to design a circuit such that the microcontroller can toggle a GPIO pin and shut the whole system (including microcontroller itself) down. And when the user presses a momentary button, the power is brought back up again.
Is this possible?
Answer
This example uses a Maxim MAX1835 step-up regulator, but could be applied to others as well that have a shutdown pin.
The circuit is normally powered down. When the user presses the pushbutton, the battery is fed into the -SHDN pin, enabling the regulator and turning on the 3.3V to the microcontroller. The microcontroller then puts a logic 1 on the POWER ON lead, holding the power on after the user releases the pushbutton. When the microcontroller wants to shut itself off, it sets the POWER ON lead to 0.
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