• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 29 subscribers
  • Views 136 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV8308: How is speed control performed in closed-loop mode?

Tom Lin
Prodigy 30 points
Part Number: DRV8308

I am using the DRV8308 to drive a DC brushless motor in Clock Frequency Mode with speed closed-loop control enabled. I want to change the motor's speed, so I adjusted the frequency of CLK. However, instead of smoothly transitioning to the new speed, the motor is experiencing jitter.

Question 1: Is it possible to adjust the speed in speed closed-loop mode, or is it limited to a fixed speed?

Question 2: If speed adjustment is allowed, is the method to change the CLKIN frequency? How can I eliminate the jitter?

  • 0
    TI__Genius 13185 points

    Hi Tom,

    Tom Lin said:
    Question 1: Is it possible to adjust the speed in speed closed-loop mode, or is it limited to a fixed speed?

    In closed-loop mode the speed of the motor can be adjected by the input frequency into the CLKIN pin. The frequency needed for a specified speed will depend on the setting of register FGSEL:

    - If FGSEL = 00b F_CLKIN = RPM / 60 * (N_POLES / 2)

    - If FGSEL = 01b F_CLKIN = RPM/60*N_FG

    Please see section 8.2.2.3 for more information.

    Tom Lin said:
    Question 2: If speed adjustment is allowed, is the method to change the CLKIN frequency? How can I eliminate the jitter?

    For recommendations on how to reduce the jitter of the motor please refer to section 1.1 of the DRV8308 tuning guide, specifically the Flutter Meter section. If you are using a FG circuit please refer to section 8.1.3 of the DRV8308 datasheet for information on reducing noise in the FG circuit.

    Regards,

    Joshua