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DRV8711 Stall Detection

liur
Prodigy 180 points
Other Parts Discussed in Thread: DRV8711

Hi, 

We use DRV8711 to drive a NEMA23 stepper motor, the internal stall detection is employed to avoid hard collision, all of parameters are adjusted to suitable value and the function is okay, however, sometimes ago we made a small mass production and found that it did not work, no matter how I adjust the registers, the stall detection always fail. neither the software nor PCB layout is changed, we cannot find out the root cause, Is it probably caused by chip production lot?

The internal stall detection parameters:

SMPLTH=1, SDCNT=1, VDIV=2, SDTHR=100, MICROSTEP=8, VELOCITY=128000pps

Thanks and Regards.

Liur

  • 0
    TI__Guru** 114905 points
    Hi Liur,

    We will investigate and reply soon.
  • 0 in reply to Rick Duncan
    TI__Guru** 114905 points
    Hi Liur,

    At 128000pps, the stall detection may not work.

    There is only 8us for the current to reach zero, connect the stall detection circuit, and measure the value. At the beginning of the next step pulse, the circuit is disabled.

    The stall detection is designed to operate at <9000 pps. Above that, it may not work.

    Assuming Microstep = 8 is 1/256 microsteps, please try lowering the microsteps to 1/16 and velocity to 8000.
  • 0 in reply to Rick Duncan
    Prodigy 180 points

    Hi Rick Duncan,

    Thanks for your kindly help. We repeat the test procedure but the stall detection still not work, it always report  stall on the motor deceleration stage,  even if we set the speed less than 9000pps, the parameters is following:

    Microstepping =1/8,  6400~12800pps, SMPTLH=3, SDCNT=1, VDIV=1~2, SDTHR=60~120;

    The previous test record show that stall detection work well using above parameters, but now it always fail. 

    Is it helpful to change the stall detection mode from internal to external?

    Thanks!

    Liur

  • 0 in reply to liur
    TI__Guru** 114905 points
    Hi Liur,

    Please see screen captures in post e2e.ti.com/.../560587

    The bemf information is not valid if the BEMFVn signal goes low because the STEP input has changed. Once the step input changes, the indexer is no longer at the zero current step.

    I am not sure how it worked will in previous test record.