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DRV8848: Some problem with Using PWM control

user4183613
Prodigy 50 points
Part Number: DRV8848


I use the following circuit.

I think port PWM_IN1 = PWM(10kHz),PWM_IN2 = 0,Motor = Forward;

 port PWM_IN1 = 0,PWM_IN2 = PWM(10kHz),Motor = Reverse;

But in fact，is not work。What‘s wrong?

Thanks！

  • 0
    TI__Guru** 114905 points

    Hi user4183613,

    Have you monitored nFAULT when trying to operate the outputs? 

    The DRV8848 is intended to drive inductive loads. Driving a large capacitor may lead to overcurrent events.

    Please remove the 220uF capacitor, and try again.

  • 0 in reply to Rick Duncan
    Prodigy 50 points

    This is really something, it works very well now.The reason is that capacitor.I changed it to 100nf。Thank you very much for your suggestion.

  • 0 in reply to Rick Duncan
    Prodigy 50 points

    One more point，I found nFAULT was pulled down from the beginning.But I think voltage, current and temperature are normal.So I've always been puzzled.

  • 0 in reply to user4183613
    TI__Guru** 114905 points

    Hi user4183613,

    Do you have a pullup resistor on nFAULT? This is required because nFAULT is an open drain output.

    From the Pin Functions Description section:

    Pulled logic low with fault condition; open-drain output requires external pullup


    If you have an external pullup, is nFAULT pulled low then released every 1.6ms. You may still be experiencing an overcurrent condition with a 100nF capacitor.

    Please monitor the nFAULT pin and use Table 2 as a guide to what type of fault you may be experiencing.