• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 30 subscribers
  • Views 367 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

DRV8256: DRV8256EPWER how to implement SLOW DECAY function

Cherry Zhou
Mastermind 22235 points
Part Number: DRV8256
Other Parts Discussed in Thread: DRV8840,

Issue:

The DRV8256EPWER does not implement the DECAY function even though it has the DECAY pin,  the detailed information of pin as follows:

But DRV8840 has the SLOW DECAY function:

The customer would like to know how to make DRV8256EPWER work in SLOW DECAY mode.

Thanks!

Best Regards,

Cherry Zhou

  • 0
    TI__Guru 56650 points

    Cherry,

    DRV8256E and DRV8256P are two different device.

    Frist, please clarify which device do you pick?

    And then, check do you drive a brushed motor or one coil of stepper motor? 

    If you drive a brushed motor, the motor speed decides the load current which may not reach the regulation point. 

    If you drive a stepper motor and the load current reaches the regulation point, you can select smart tune ripple control decay to achieve the slow decay (two low side FETs are on after the output current reaches the regulation point.

    Regards,

    Wang Li

  • 0 in reply to Wang5577
    TI__Mastermind 22235 points

    Hi Wang,

    Thanks for your reply!

    The customer provides some info:

    Device: DRV8256E(PH/EN). Motor: brushed DC motor.

    And the customer would like to figure out how to make the DRV8256E implement the Slow Decay effect of the DRV8840.

    Could you please help to check this?

    Thanks a lot!

    Best Regards,

    Cherry

  • 0 in reply to Cherry Zhou
    TI__Guru 56650 points

    Cherry,

    First let us check DRV8840 bridge control: the decay pin selects slow decay and fast decay at ENBL=0. In what condition, does the customer set slow decay mode?

    DRV8256 doesn't have slow decay if the current doesn't reach the current regulation point. If the output current reach the current regulation point, the ripple control decay mode make DRV8256 run on fixed ripple amplitude slow decay, instead of traditional fixed TOFF slow decay.  

    Regards,

    Wang Li