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DRV10983-Q1: Help with strange behavior

Mitchell
Expert 4915 points
Part Number: DRV10983-Q1

Hi Team, 

My customer is working on a design with the DRV10983-Q1 and is noticing some odd behavior that we're having trouble explaining.

What they are noticing is that in order to get the motor to spin up in closed loop mode, they have to disable the lock2 for Abnormal Kt. The problem is that we can't figure why this flag keeps getting set in the fault reg. They have gone through their calculated Kt several times and it's set close (enough) to the measured Kt value. Also, they've ensured that the KtLckThr is at the widest range. 

See the register settings below:

##Mass read 0x90 -> 0x96
0xdd03
0xbb1f ##sets Kt to 27.6 (also tried other values)
0x0050
0x9a25
0xa93b
0x43b0 ##sets KtLckThr to 11
0x0a51

##while motor is running at constant speed
i2cset -y -f 1 0x52 0x00 0x0001 w ##clear fault reg
i2cget -y -f 1 0x52 0x00 w
=>0x0400
i2cget -y -f 1 0x52 0x03 w ##read Kt
=>0x5300 ##decode to 37.8

Any feedback or thoughts you have on what's going on would be extremely helpful.

Thanks,
Mitchell

  • 0
    TI__Expert 6065 points

    1) Abnormal Kt lock is commonly ignored, as the calculation of kt is just a rough estimate. So as long as none of the other locks dont trigger, you should be fine. 

    2) Please confirm if these are your settings below.

    If these are your settings I would recommend the following:

    a) It doesnt seem like abnormal kt lock detect threshold (KtLckThr) is set to the max range, I would set it to kt_high = 2Kt, kt_low = 1/2kt. Once you do this, then the measured kt of 37.8mV/Hz will be in the range of kt_high = 2Kt = 2*29.7, kt_low = 1/2kt = 1/2*29.7

    b) I would enable the speed abnormal lock and open loop stuck lock

    c) You seem to have closed loop disabled in the settings you gave me. You should enable closed loop.

    3) If you still have concern about kt not matching, I would look at the phase current to make sure that it is evenly sinusoidal. If it is, it most likely means you are spinning the motor properly, and can confidently ignore the kt mismatch.