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DRV8889-Q1: whether the following 3 functions are available when drv8889q1 is applied to stepper motor driving?

Part Number: DRV8889-Q1
Other Parts Discussed in Thread: DRV8904-Q1

Hi, Team

1. The back-EMF of stepper motor could be read no matter stalling happens or not.

2. Constant Voltage Drive mode is available under the Full step or Half step driving conditions.

3. Constant Current Drive mode is available under Micro stepping condition and the Constant Current could be regulated as we want.

I need to examine the 24stepper motor and do not know DRV8889Q1 can satisfy those requirements or not, if DRV8889q1 cannot, what IC of TI can take these? 

Best Regards,


  • Hi Leo,

    Constant current level can be adjusted by TRQ_DAC. (Page 25). 

    1. Back EMF information used in DRV8889-Q1 for stall detection etc. Can not be read form outside.

    2.DRV8889-Q1 output is always PWM, not constant voltage. So output shows 0V or VM pulse driving. ON/OFF time is adjusted to meet target current level(ITRIP). Please refer datasheet page 24 Fig 7-8 for current waveform example. Basically PWM is ON during tDRIVE.

    3. Yes.

    DRV8889-Q1 support more that 24steps (2,4,8,16,32,64,128,256 : Please refer page 16 table 7-2). However if customer needs exactly 24 steps, controlling VREF with an MCU DAC could be option.(Please refer page 18 Fig 7-3). No TI device to support 24 step.

    I guess 16 step or 32 step could be OK for customer.



  • Thank you for your answer, Shinya.

    Additionally, you had mentioned that 'ON/OFF time is adjusted to meet target current level' , and I wonder whether it can set the ON/OFF time(or the duty ratio) of the PWM output to some one constant value, and lock it, instead of changing duty ratio of PWM to meet target current automatically.   I mean, the equivalent DC voltage of PWM output could be constant and fixed, not the current being adjusted to one fixed value.

    Or setting the target current level to 100% directly may be a feasible method to achieve my goal of Equivalent Current Voltage output?

  • Hi Leo,

    Based on your feedback and what you want to drive, DRV8889-Q1 does not work such a way. It does now work with fixed PWM duty by ignoring motor current. If duty 100% setting, output keeps VM voltage level 100%. I think it does not work for you.

    I would suggest to check DRV89xx-Q1 (e.g DRV8904-Q1). This device can set target fixed PWM duty via SPI (255 step resolution. Table 40 datasheet page 86). So you can provide target duty %. It is not DC voltage, but can control equivalent voltage level.

    However need to keep updating target PWM duty via SPI to rotate stepper motor.



  • Hi Shinya,

    You mean, if the duty 100% setting, the Voltage of the output could always be the same as the VREF? (or VM represents some other Constant value?).    If yes, DRV8889Q1 will be OK.  I do need to set the output voltage to 100% with ignoring motor current, which is exactly what I really want.

    But the point is  Can the MOSFET tolerate the full current's passing through and 100% level VM voltage  for a long time?(maybe several seconds)

  • Leo,

    The device will always try to regulate the current based on STEP input.  There is no way to "ignore" the motor current and bypass this loop.