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Does DRV8711 have hold current?

dh Paeng
Prodigy 100 points
Other Parts Discussed in Thread: DRV8711

Hi~

I'm using DRV8711.

I don't have problem when I move motor, but I have problem when I stop motor.

I want to use hold current  while motor is stop.

If I motor running, motor must not move.

So I didn't send pulse step to pin(STEP / AIN1).

And I changed only CTRL Register Address (BIT0 : 1 Enable motor)

 

Motor wasn't run, but sound was noise.

So I changed TORQUE(0x12 -> 0x01), but I can hear noisy sound too.

 

TORQUE = 0x12

 

TORQUE = 0x01

 

I don't want to hear noisy sound.

I want not to move using hold current.

How can I do?

 

  • 0
    TI__Mastermind 26065 points
    Hi Paeng,

    The key to reduce the audio noise is to set the decay parameters so that the current ripple during the regulation is as small as possible.
    So we can do setting that make the regulation PWM frequence higher, using more SLOW decay portion. Could you look up note www.ti.com/.../slva637.pdf
    to get better idea of how the decay parameters affecting the current regulation. Section 6.1 give some example on how to make the ripple smaller.

    Best regards,
  • 0 in reply to Wilson Zuo
    Prodigy 100 points

    Hi, Zuo.

    Thank you for your reply.

     

    I want know stop current information, not run current.

    Because I have a little problem in running motor and I knew that document.

     

    Let me explain.

    I gave current to motor when motor don't move.

    I run forcibly motor when motor stopped, motor must doesn't move.

    Because I'm giving hold current to motor.

    And I don't want to hear noisy sound at that time.

     

    Do you need other explanation?

     

    Thank you.

     

  • 0 in reply to dh Paeng
    TI__Mastermind 26065 points
    Hi Paeng,

    Yes. That is the noise coming from the the chopping current. The ripple of the current gives the noise. Slow or mixed decay, and the higher chopping frequency gives less current ripple and less noise. But maybe it is not totally avoidable. Pay attention that if you use only Slow decay when the motor is holding, it may have the out-of-regulation problem, depending on your motor parameters.

    Best regard,
  • 0 in reply to Wilson Zuo
    Intellectual 710 points
    Paeng,

    If you want your hold current to be less than your running current then reduce your TORQUE value in the TORQUE register (0x01) when the motor is stopped. You'll need to set it back to the running value before you start moving again. For a coarse adjustment you also could use ISGAIN in the CTRL (0x00) register if you aren't already at the lowest gain.

    As WZ said, if you want to change the audio levels you need to change your timing parameters. If you look at the phase current when you hear the noise you'll be able to see the frequency content responsible for the noise.
  • 0 in reply to Wilson Zuo
    Prodigy 100 points

    Hi~ Zuo

    Thank you for your reply.

     

    I have a question.

    Now I use control that not gives chopping frequency (STEP / AIN1) for motor hold.

    and only use CTRL REGISTER(ENBL = 0x01).

    Because motor have current and it must don't move.

     

    If you know another method, please tell me.

     

    Thanks.

  • 0 in reply to John Duquette
    Prodigy 100 points

    Duquette,

    Thank you for your reply.

     

    I already controlled TORQUE register value(0x00~0xff). but audio level was same.

    I didn't control ISGAIN. I'll try that.

     

    My first wave form image is phase current.

    I didn't use PWM, so I couldn't see frequency.

    Because motor must do not move when motor is stopped.

    To do that, I shoud don't use STEP / AIN1 and I should use only parameters.

     

  • 0 in reply to dh Paeng
    Intellectual 710 points

    "I already controlled TORQUE register value(0x00~0xff). but audio level was same." - Are you sure your change was working?  You should see the amplitude of your current change when you change the TORQUE value and that should effect your sound level.  

    "I didn't use PWM, so I couldn't see frequency." - Even when running with the indexer the controller is still using PWM and that is the frequency you are hearing.  Zoom in closer in time on your scope and you'll see the frequency you are hearing.  See that slight discontinuity at the zero crossing?  You need to be on a time scale to show the cycles around that to see how your parameters are defining an audible frequency.  Then adjust your trigger level to look at the top of the sine wave for the best look at the audible components.  

    The attached plot shows poor parameters with about a 2 KHz (0.5 ms) audible noise:  

  • 0 in reply to John Duquette
    Prodigy 100 points

    I think that you don't understand my mean.

     

    See the below picture.

    I want that motor does not move.

    Even if I move motor, motor must doesn't move.

    So I didn't give signal (STEP pin) and I changed Register.

    CTRL Register Address = 0x0h (1: Enable motor)

    TORQUE Register Address = 0x1h (0x00 ~ 0xA0)

     

    I measured current at A phase.

    You can see waveform. TORQUE Register Address = 0x1h (0x00 ~ 0xA0)

    I didn't move motor,  I couldn't see frequency.

     

    I want reduce audio level when motor stop. 

     

  • 0 in reply to dh Paeng
    TI__Guru** 114905 points
    Hi Paeng,

    Do you know where the indexer is in the step table when you stop the motor?

    As an experiment, can you stop the motor at a location where the current is 100% in one winding and 0% in the other? This should reduce the noise further.
  • 0 in reply to dh Paeng
    Intellectual 710 points

    So I expect your audio volume increased as you ramped from 0x30 to 0xa0.  Is that correct? 

    If so, zoom in farther on that fuzz in your zoomed trace.  A repetitive pattern there in the audio frequency range is your noise source. 

    If not, it doesn't make sense you have motor noise.  Is the noise coming from the controller PCB?  You could have a capacitor with a piezoelectric effect making noise.