Active low shutdown options

Using Arduino Microcontrollers
1

I am using a Adafruit Power Boost like this to charge a 3.7V LiPo and Also boost it to 5V when using as a standalone based on battery power : PowerBoost Schematic

If you notice this module shuts down when the Enable pin is grounded. Now i want to be able to do this with a solid state device ( i know its pretty easy with a mechanical relay ).

I am using this module to power a Mega2560 board and the board sleeps most of the time to save power.

I want to be able to use a MCU pin to shutdown this module when the MCU goes to sleep without using a mechanical relay. Any ideas ??

Thanks

2

When you

digitalWrite(ShutdownPin, LOW);

The ATmega2560 will connect that port to ground. If the current draw on this port would exceed the Absolute Maximum Ratings, specified on page 355 of the datasheet, you can use an NPN transistor, connecting the Power Boost enable pin to the collector, the MCU port to the base and the emitter to ground. Depending on which transistor you select, or trasistor IC, you may need additional biasing resistors etc. In this case you would:

digitalWrite(ShutdownPin, HIGH);

I don't believe the current draw will exceed the Absolute Maximum Ratings, but you can test this by setting your multimeter to measure current and connecting the positive lead to the enable pin and the negative lead to ground. The meter should not read more than 20 mA, assuming you are running the Mega2560 on 5.2 Volts DC.

3

Perehama:
When you

digitalWrite(ShutdownPin, LOW);

The ATmega2560 will connect that port to ground. If the current draw on this port would exceed the Absolute Maximum Ratings, specified on page 355 of the datasheet, you can use an NPN transistor, connecting the Power Boost enable pin to the collector, the MCU port to the base and the emitter to ground. Depending on which transistor you select, or trasistor IC, you may need additional biasing resistors etc. In this case you would:

digitalWrite(ShutdownPin, HIGH);

I don't believe the current draw will exceed the Absolute Maximum Ratings, but you can test this by setting your multimeter to measure current and connecting the positive lead to the enable pin and the negative lead to ground. The meter should not read more than 20 mA, assuming you are running the Mega2560 on 5.2 Volts DC.

The issue is really not about the loading on the port pin of the MCU. The issue is when the MCU pulls the pin to Ground the Power Boost module shuts down the 5V to the MCU !! So with the MCU going off the grid, i dont what will happen to the Port Pin