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DRV8308: speed control

Cherry Zhou
Mastermind 22235 points
Part Number: DRV8308

Hi Team,

Use CLKIN signal frequency mode. When the speed is closed, the customer would like to control the speed of the motor by changing the size of the frequency, but the speed of the motor will become a jerkic change, which is not a smooth transition.

Could you help tell can the CLKIN change the input frequency directly when in signal frequency mode?  And how to modify the registers to have the speed transition become smooth? Thanks.

Best Regards,

Cherry

  • 0
    TI__Genius 12215 points

    Hi Cherry,

    Cherry Zhou said:
    can the CLKIN change the input frequency directly when in signal frequency mode?

    In closed-loop mode the speed of the motor can be adjusted 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 equals 00b, F_CLKIN = RPM / 60 * (N_POLES / 2)

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

    Please see section 8.2.2.3 of the datasheet for more information.

    Cherry Zhou said:
    how to modify the registers to have the speed transition become smooth

    For information on tuning please refer to section 4.2 of the DRV8308 User's Guide. For an explanation on the effect of some registers please refer to this E2E post and this E2E post.

    This device can be tricky to tune for some motors. I would recommend looking at our MCx8329 devices as these are external FET, integrated control, and much simpler to tune. If you would like a recommendation better suited to the customers application please provide the nominal voltage, power requirement, application, desired commutation, and if sensored or sensorless is required.

    Regards,

    Joshua