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DRV8818: About the motor noise

John Cheng17
Prodigy 100 points
Part Number: DRV8818

Dear Expert,

 

My customer have application problem about DRV8818, please kindly help.

 

They are using DRV8818 to drive a step motor, the spec of motor as below:

The circuit as below:

Software set to 7000pps, the motor rotate form position A to position B need 1200 pules. The problem is the motor has making acoustic noise, even the motor not running.

The current curve of one phase as below:

When the motor not running, it still making noise, the voltage curve as below:

They have tunning the VREF, but doesn’t have any improvement. Please help, Thanks!

  • 0
    TI__Guru** 114905 points
    Hi John,

    Can you describe what "even the motor not running" means?
    Does the motor start and then stall?
    Does the motor not start?

    What is the starting pps for the motor?
    Does the customer start at 7000pps or accelerate to 7000pps?
    If using an acceleration rate, what is the acceleration?

    Has the customer checked the current in the second phase?
  • 0 in reply to Rick Duncan
    Prodigy 100 points

    Hi Rick,

    Very glad to recieve your reply.

    "even the motor not running" means both of your description.

    The curve was captured after the drive board power on, and the motor was not rotate.

    I'll check the other information to customer.

    Thanks.

    John

  • 0 in reply to Rick Duncan
    Prodigy 100 points

    Hi Rick,

    I,ve got the update from customer.

    The motor was start from 2000pps accelerate to 7000pps.

    Acceleration 500000p/s^2

    They using same code drive A3983 that was quiet but DRV8818 has noise.

    Attached file was A3983 datasheet

    A3983_datasheet.pdf

  • 0 in reply to John Cheng17
    TI__Guru** 114905 points
    Hi John,

    There are similarities in the two devices, but there differences also.

    The DRV8818 has many tuning options (RCx and DECAY).

    Assuming the A3983 ROSC pin is set to >3V, please adjust the following to achieve similar timing:
    RCx to 44.2k and 680pF
    Decay to 1.45V

    This should be timing that is similar to the A3983, and should be a good starting point for comparison.

    If the toff is adjusted using ROSC, the values above can be adjusted as well using the equations in the DRV8818 datasheet.
  • 0 in reply to Rick Duncan
    Prodigy 100 points

    Hi Rick,

    Thanks for your help, I'll send these message to customer.

    John