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DRV8889-Q1: design problem

Colt Zhang
Expert 3870 points
Part Number: DRV8889-Q1

Tool/software:

hi expert,

my customer use GUI to control DRV8889-Q1 and find the big noise about step motor.

customer want to know  how to understand the Torque, how to set this , and what specific impact does this parameter have on the output parameters.

  • 0
    TI__Mastermind 29505 points

    Hi Colt,

    Torque setting is the TRQ_DAC bits setting in the CTRL1 register. It is only an additional scaling along with the VREF input for setting the coil currents. For example with the Full Scale current setting of 0.2 A, Torque setting of 25% will result with 0.2 * 25/100 =  0.05 A. This is a very low current, the motor may not be running correctly with this. 

    For a 0.2 A current rated motor, if the Full Scale Current was set at 0.2 A then Torque must be 100%. If the Full Scale Current was set at 0.8 A then Torque must be 25%. The end result will be the same. See section 7.3.5 Current Regulation, page 20-21 of the DRV8889-Q1 datasheet. I hope this helps to understand Torque settings. 

    Colt Zhang said:
    my customer use GUI to control DRV8889-Q1 and find the big noise about step motor.

    I noticed the target speed was set at 21000 as well as starting speed the same which means no ramp up acceleration. This may be the issue for noise and likely the motor may not be running at all. I think the customer must set the starting and stopping speed to 1000 or 2000 PPS. The acceleration rate can be set to 10000 PPS-PS. Please try with these settings. Also if you could share a coil current A or B, captured with an oscilloscope and current probe will be helpful to analyze the situation. I assume VM = 12V. Could you please share the stepper motor specifications, its datasheet? How many steps per revolution and speed-torque plot will be important to review. Thank you.

    Regards, Murugavel