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DRV8307: DRV8307 about the Locked Rotor issue and PWM control issue

Mickey Zhang
Genius 12080 points
Part Number: DRV8307

Hi Team,

The customer is using DRV8307. He has some qusestions as belows.

Q1: Locked Rotor question:

The customer refer to 7.3.11.6 Rotor Lockup (RLOCK) of the datasheet.  If the motor is needed to stop operation normally, is this situation considered a fault? 

If  this situation is considered a fault, then the motor is locked and is disabled. The part  will re-enable itself after a fixed delay of 5 s. Is this understanding  correct?

Q2: PWM control question:

The 8.2.2 Detailed Design Procedure of the datasheet shows if the PWM duty cycle is changed while spinning, use gradual steps (for example, 1% increments).

 If  this means DRV8307 cannot support the abrupt change of the PWM duty cycle?

If  DRV8307 cannot support  the abrupt change of the PWM duty cycle, but the customer needs the the PWM duty cycle to change abruptly, such as quickly track position or speed commands, how to deal with this issue?

Q3: LOCKn pin question:

Does  the LOCKn pin function mean the motor speed closed loop is locked?

If  the LOCKn pin function means the motor speed closed loop is locked and the customer does not want to use the lock function, can the LOCKn pin be disabled?

Q4: Is DRV8307 suitable for the frequent commutation of the motor occasion and  the frequent start and stop of the motor occasion?

Q5: Is DRV8307  suitable for the position servo control? The position signal is a square wave step signal.

Best Wishes,
Mickey Zhang
Asia Customer Support Center
Texas Instruments

  • 0
    TI__Guru** 114905 points
    Hi Mickey,

    Our expert on this device has been notified and should reply soon.
  • 0 in reply to Rick Duncan
    TI__Expert 4650 points

    Hi Mickey,

    Responses to the customers questions are below.  

    Q1: Locked Rotor Question

    RLOCK is considered a FAULT.  For normal stopping operation, the motor should not flag an RLOCK fault.  If the BRAKE pin is used to stop the motor, the PWM signal should be brought to zero as well.  This will allow for normal operation of the device.

    Your understanding is correct, the device will restart after 5s.

    Q2:  PWM Control Question

    Depending on the motor selected by the customer and the intended load for their application, they may be able to increase the speed in large steppers.  The main concern is locking the rotor due to large step changes in commutation.  

    Q3:  LOCKn Pin Question

    For the DRV8307, the LOCKn pin will be pulled low when the motor has reached a constant speed.  This device operates in open loop at all times.  If the customer does not want to use the LOCKn pin, it can be left floating in their design.

    Q4: This device should be suitable for this application.  For faster starting and stopping, see section 8.1.3 of the datasheet.

    Q5:  This device should be suitable for position control.