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I want to control the power supply of a sensor with a microcontroller, so I can turn it off when it isn't being used. My goal is to minimize power consumption on a battery-powered device.
Both the microcontroller and sensor are running on 3.3 V.
Can I use a single MOSFET directly driven by the controller? Or is there a better method?
atmega328p micro controller and GY 61 accelerometer sensor are used.
Probably- one method would be to use a P-channel MOSFET as a high-side switch to control the 'sensor' power. You might have to add a pull-down or otherwise ensure that the output of the 'sensor' was close to 0V with no power- if it is allowed to float around the MCU power consumption might increase.
There are many inexpensive logic-level MOSFETs that will work fine from -3.3V gate voltage with guaranteed very low Rds(on) and reasonable guaranteed leakage.
simulate this circuit – Schematic created using CircuitLab
You may have to ensure that the 'sensor' supply has some series impedance or that the MOSFET does not switch too rapidly if the 'sensor' has large bypass capacitance- otherwise it could glitch the MCU power when it turns on and cause problems.
You may have a simpler option. If the sensor's maximum current requirement is low enough, you can use a digital output (from your microcontroller) to power the sensor directly.
Check the following things:
If you update your question with the part numbers of your microcontroller and sensor, we can give you specific examples.
You did not specify sensor type or its power consumption, but here are some options:
You can use a dedicated power switch chip, for example: TI load switches. They can also come with overcurrent protection, so if your sensor is dangling on a cable outside and you short power to ground it will not disable your device.
You can use a separate LDO with an ENABLE pin to disable power delivered to the sensor (for example MIC5205).
If the sensor is consuming very little power (below <10mA - check your MCU pin specification) you can just power it directly from a GPIO when needed (CHEAPEST).
I'll add a cheap ghetto solution:
If your sensor draws a small current (like a few mA) you can use a good old-fashioned logic gate as a switch. Pick one with high drive strength, like 74AC or 74LVC.
Hell, you can even use an IO from your micro. Or a pin from an I2C IO extender if you have one in your design.
This is obviously not for every situation, but when applicable, it does allow you to switch several loads with a single chip, and it is cheap and compact.
