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Original question:

DRV11873: Time to start switching/COM pin

DRV11873: Drive brushless electric machine by DRV11873

user6041964
Prodigy 20 points
Part Number: DRV11873

Drive the hard disk motor with DRV11873，It is found that when the motor starts, the direction of rotation is random。If the motor starts in the right direction of rotation, it can work properly.

If the motor starts not in the right direction of rotation, it will run at low speeds in the wrong direction with 70% duty cycle test。

With 10% duty cycle test, the motor stops and goes, and eventually moves in the right direction.

No matter what the duty cycle is, if we set a right direction for it by hand, it will run properly.

  • 0
    Prodigy 20 points

    Hi team,

    this motor without hall sensor。where is the problems.


    Best regards
    hongbo

  • 0 in reply to user6041964
    TI__Mastermind 24405 points

    Hi,

    Thanks for posting in MD forum!

    DRV11873 has an FR pin to set the motor for forward or reverse spin. During DRV11873 power up, FR status is set. During normal operation, the spin direction of the motor does not change if the FR status is changed. The FR status can be reset if the PWMIN is pulled low; if FS is high, PWM must be pulled low for 300 µs, and if FS is low, PWM must be low for 600 µs. After being pulled down for the appropriate time, the FR status resets upon the PWM rising edge.

    Can you check your FR pin? Make sure the pin is set high for reverse rotation. Set low or floating for forward rotation.

    Regards,

    Vishnu