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DRV8889-Q1: DRV8889 EVM design

Kygo Cheng
Expert 6830 points
Part Number: DRV8889-Q1

Hi Team,

DRV8889 cannot read the torque value at 10V ~ 9V,
I have measured that the frequency of the VCP waveform is not 400KHz. Will this have any effect?

  • 0
    TI__Guru 56650 points

    Kygo,

    On the waveform, which one is the torque count? Do you test it on an EVM?

    On DRV8889-Q1EVM, there is torque count test point. The lowest torque count bit is equivalent to 12.9mV on that test point. You can read the torque count from that point. Also, show it on the waveform.

  • 0 in reply to Wang5577
    TI__Expert 6830 points

    Hi Team,

    Reply to your question:

    1. On the waveform, which one is the torque count? Do you test it on an EVM?

    >>> No, this is  data measured on customer PCB

    More question:

    2. Could you explain to me whether DRV8889 can read the value of RQ_COUNT, it depends on those necessary factors,
    In other words, without those conditions, DRV8889 will not be able to generate RQ_COUNT value ,THX

    3. In addition to the conditions below, are there other factors?

  • +1 in reply to Kygo Cheng
    TI__Guru 56650 points

    Kygo,

    If nSLEEP is high and VM voltage is higher than UVLO threshold, TRQ_CNT is just a register which can be read out any time, even it is zero (motor is not spinning); EN_STL is zero.

    To make TRQ_CNT have a correct value, we have to select smart tune ripple control decay.

    To make stall detection work, we have to set "EN_STL" bit to "1".

    Regards,

    Wang Li