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Drv8811 output frequency

Adesh Jagtap
Intellectual 320 points

I tested my stepper motor using mcu and certain frequencies... I also check waveforms of output  given by internal H-bridges at full step and other modes also but I am getting output frequencies are getting lower as I go from to 1/8th step ....can anyone explain relationship between frequency of step input and output of H-bridges???

  • 0
    TI__Mastermind 26065 points
    Hi Adesh,

    Do you mean the "frequency" as the speed of motor?
    Note that the one input step refers to one FULL step@FULL step mode, and refers to one micro-step@ micro-step mode.
    So if the input step frequency is not changed, the speed of motor will be half of the speed when only change the micro-stepping level to a higher level, such as from Half to 1/4.

    The H-bridge output frequency is based on the motor parameters and decay modes parameters, The device uses fixed OFF time scheme but that is only part of the PWM period.

    Best regards,
  • 0 in reply to Wilson Zuo
    Intellectual 320 points
    Hi Wilson,
    I tested all output waveforms which were given to motor coil. I got different frequencies in full step, half step, 1/4th ,1/8th step. But I didn't understand logic behind this...can u pls explain step frequency is related to that output waveform frequencies?
  • 0 in reply to Adesh Jagtap
    TI__Mastermind 26065 points
    Hi Adesh,

    I'm a little confused on your means of "output waveform frequencies". Do you mean the output PWM seen from the OUTx pin or just the motor's running frequency/speed.

    Could you give waveform to explain you question?

    Best regards,
  • 0 in reply to Wilson Zuo
    Intellectual 320 points
    hello Wilson,
    I mean output PWM seen from OUTx pin.....Actually I connected two output port BOUT1 and BOUT2 to oscilloscope...