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DRV8711 maximize output current

Pascal Kneuper
Prodigy 10 points
Other Parts Discussed in Thread: DRV8711

Hello,

i want to drive a 2mH stepper motor via the DRV8711. I'm currently controlling the driver with an Arduino MEGA.
For our purposes we want to drive the motor with

  • 2,67A max current
  • using half step
  • step frequency of  7kHz
  • supply voltage of 38V
  • 400 steps a time, small rest period afterwards

I'm unable to achieve the desired amperage on higher frequencies (maximum possible current at the moment: 2.09A). By increasing the supply voltage by 3V, the motor reaches the desired current, however this is not an option for us.

Are there any parameters I could change to increase the output current without changing the general setup?

Currently the registers are set as following

  • Toff = 0x30 = 24,5µs (default)
  • Tblank= 0xFF = 5,12µs, adaptive blanking time enabled
  • Tdecay = 0x10 = 8 µs (default)
  • Decaymode: Auto mixed decay at all times

I will gladly provide more information.

Thanks in advance,


Pascal

  • 0
    TI__Guru** 114905 points
    Hi Pascal,

    You may be reaching the limit of the motor. The back EMF may be preventing the desired current level. As you observed, raising the voltage is the best approach to reach the desired current.

    There are a few items to try:

    1) Change to slow decay on increasing, and mixed or automixed decay on decreasing.
    2) Lower the step frequency. This will allow more time for the current to reach the desired level.
    3) Talk to your motor manufacturer about alternate motors.