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MSP430FR2311: GPIO pin floating during sleep mode

gaurang kuchhal
Prodigy 80 points

Part Number: MSP430FR2311

I am using MSP430 GPIO pin to drive a load using MOSFET as shown in below photo.

This GPIO pin turns on the MOSFET in response to an external interrupt on another GPIO pin. When there is no interrupt, the MCU is in sleep mode.

Sometimes when this circuit is left overnight without any external interrupt, the GPIO pin driving the MOSFET charges up and falsely turns on the load. 

My question is : Is it expected for the GPIO pin to charge up when the MCU is sleeping? This pin is defined as Output in the initial system setup. What can be the best way to fix this issue?

My thoughts : A simple fix can be to pull the GPIO pin low externally but now the PCBs are made and that is not possible. This GPIO pin is configured as output, so from my understanding using internal pull down resistors is also not an option.

  • 0
    TI__Guru 71216 points

    Hi Gurang,

    Yes, typically when interfacing an MCU to a MOSFET you want a series resistor to limit the surge current caused by the internal capacitance on the gate, plus you want a resistor from the gate to ground to keep the MOSFET off in case the MCU is not power or during bootup when the pin has not been configured yet.

    Now, that said, if you have the pin configured as an output and driven low overnight, I'm not sure where the charge is coming from.

    One option is to enable the internal pull-down resistor on that pin to see if that will help.

    From the FR2311 family user's guide:

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