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DRV8412: How to make mode configurable?

haras nosregor
Prodigy 90 points
Part Number: DRV8412

Tool/software:

I'd like to be able to change the logic levels of M1 and M2 using a microcontroller. My first idea is just to connect the M1 and M2 pins to digital outputs on the microcontroller. However, it seems like doing so would violate the recommendation in section 3.4.4 of the datasheet: "Mode select pins (M1, M2, and M3) should be connected to either VREG (for logic high) or AGND for logic low." 

What is the reasoning behind this recommendation and what is the best way to make the mode pin logic levels configurable?

Thanks,

Sarah

  • 0
    TI__Mastermind 44665 points

    Hi Sarah,

    The absolute maximum ratings for these pins are –0.3 V MIN and 4.2 V MAX with respect to AGND. So applying a 3.3 V logic high or AGND (0 V)  logic low should work. 

    The mode control logic block sits in the AGND and VREG power domain of the IC. Hence the section 3.4.4 recommendation.

    The VIH and VIL for these pins are as below. So a 3.3 V for high and 0 V for low with respect to AGND should work assuming MCU GPIO could assure this. I hope this is helpful. Thank you.

    Regards, Murugavel 

  • 0 in reply to Murugavel4637
    Prodigy 90 points

    Hello,

    Thank you for the response. The signal from the microcontroller will be 3.3V logic high or board ground (0V) logic low, not AGND logic low. Should I remove the 1 Ohm resistor from AGND to board ground if I am doing it this way?

    The other option I see is to use a FET to pull the mode pin to VREG or AGND. The microcontroller output would drive the gate of the FET. 

    Thanks,

    Sarah

  • 0 in reply to haras nosregor
    TI__Mastermind 44665 points

    Hi Sarah,

    haras nosregor said:
    The signal from the microcontroller will be 3.3V logic high or board ground (0V) logic low, not AGND logic low. Should I remove the 1 Ohm resistor from AGND to board ground if I am doing it this way?

    Yes, this would be a valid option.

    haras nosregor said:
    The other option I see is to use a FET to pull the mode pin to VREG or AGND. The microcontroller output would drive the gate of the FET. 

    This would work as well. You can have the FET pull-up resistor connected to VREG. Thank you. 

    Regards, Murugavel