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A short button press applies power, a subsequent press initiates orderly shutdown under control of the microcontroller, and a long button press forces power-down. The microcontroller instrument can also turn itself OFF by setting an output pin.
How does auto power off circuit work on microcontroller?
The auto power off circuit cuts off the power completely. So, there is no power consumption when the microcontroller is not executing any task. In deep sleep mode there is much less power consumption than the active mode.
How does the latch on a microcontroller work?
Subsequently, setting the output pin to an active low causes the latch to switch to its OFF state after several seconds. Ready or not, he embedded system can be forced to power down by pressing and holding the button for more than three seconds. To use the circuit optimally, the microcontroller’s application program should do the following:
Fig. 1 Circuit schematic of a latching push button ON/OFF power switch for a microcontroller based product, allowing the microcontroller to turn itself OFF. In this circuit, a momentary button press turns ON power to the microcontroller, and latches it ON. A second press can initiate shut down, or the microcontroller can turn itself OFF.
Why do you need a power switch on a microcontroller?
For controlling smart products containing microcontrollers you often want to ensure that the power is not inadvertently removed. Consequently, you want a power switch that can be turned ON by a brief button press, but requires a longer, deliberate button hold to turn it OFF.
How does the power switch work on a N-MOSFET?
While it is ON, pressing and holding the button for more than 3 seconds turns the power switch back OFF, and it stays OFF until the next momentary button press. For it to reliably turn OFF, the load should draw sufficient current so that any downstream capacitors will discharge within a few seconds, allowing the gate drive of the N-MOSFET to decay.