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DRV8889-Q1: pulse in AOUT1

Daniel Wang (auto)
Expert 3540 points
Part Number: DRV8889-Q1

Tool/software:

Hello team,

My customer met EMC issues, and found it is related with the pulse in A+/AOUT1, pls see the waveforms as below:

The waveforms were tested when the motor was stopped in certain position, in my understanding, the A+ (AOUT1) and A- (AOUT2) should be constant low, why there is such pulse? Any methods to cancel it?

Thanks

Regards

Daniel Wang

  • 0
    TI__Mastermind 44875 points

    Hi Daniel,

    Thank you for your post.

    Daniel Wang (auto) said:
    The waveforms were tested when the motor was stopped in certain position, in my understanding, the A+ (AOUT1) and A- (AOUT2) should be constant low, why there is such pulse? Any methods to cancel it?

    This is normal behavior. When the step input pulses are stopped the stepper motor would still still have hold current as per the index position it was stopped and depending on the microstep mode used. See "Table 7-3. Relative Current and Step Directions" in the datasheet page-17. This means current regulation tON and tOFF chopping will be active even while the motor is in hold. AOUT1, 2 and BOUT 1, 2 would be HiZ only when DRVOFF = 1. Usually engineers provide 4 capacitors around 10 nF, one each on AOUT1, 2 and BOUT 1, 2 to mitigate EMI as well use slower SR (slew rate) setting. Please request the customer to try these. Thank you.

    Regards, Murugavel