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MSP430FR2311: MSP430FR2311 control issue

Peter Tseng
Mastermind 6380 points
Part Number: MSP430FR2311


Hi team,

I have an issue to control the load switch with FR2311.

The block is as below.

while the battery voltage drops to 2.5V, the FR2311 I/O output will oscillate and cannot control the load switch well.

Per the FR2311 datasheet, the Vcc needs higher than 1.8V which is lower than 2.5V of battery voltage.

May I know if there is any suggestion for this issue and how to fix it?

Thanks.

  • 0
    Guru 42205 points

    Do you have bypassing for the MCU? Have you monitored the MCU VDD when the switch turns on? Have you tried it without the diode in place? How do you know the switch isn't oscillating? 

  • 0
    Guru 100785 points

    As the battery voltage drops, the internal resistance increases, so you can't get as much current out of it. If I'm reading your scope trace correctly, the voltage is repeatedly drooping from 2.5V to (maybe) 1.8V, then back to 2.5V suggesting that the MCU is resetting over and over since it can't quite get enough current to operate.

    2-minutes-with-Google suggests that a CR2032 is effectively dead when it reads below 2.7V.

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