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DRV8426: Current ripple at smart tune Ripple Control

Yusuke Mukuno
Expert 7395 points
Part Number: DRV8426


Hi Expert,

My customer found the large current ripple issue at smart tune Ripple Control.

They set Toff pin =1, Therefore they believe current ripple will be 11mA + 2% of ITRIP. (Itrip=670mA, ripple= 11mA + 2% of ITRIP = 24mA)

Current ripple on the following waveform is 48mA (on the short Toff period) 

(CH1: Vref, CH2: IA, CH3:IB)

Could you please let me know the reason of this large current ripple?

Also, this waveform has some long Toff period. (Current ripple max = 77mA)

Do you have any idea for reducing this long Toff? 

(CH1: Vref, CH2: IA, CH3:IB)

They believe, Smart tune Ripple control will be controlled between peak ripple and valley ripple.   

Why does this waveform have different Toff periods?

Thanks

Muk

  • 0
    TI__Guru 56650 points

    Mukuno-san,

    Let us debug it.

    1. The ripple got bigger in the middle of the step. I would think the motor is spinning to a certain position. Do they check it when the motor is spinning?  If the motor is spinning, can we stop or stuck the motor and check current waveform?

    2. Can we change TOFF setting to 0 and HiZ to see the ripple change? In this case, we can make sure the TOFF setting and verify how many ripple is contributed from the full scale current setting?

    3. What is the micro-stepping  setting? If the motor is spinning, can we use micro-stepping setting to reduce the motor vibration and the ripple current change? 

    4. I want to understand is it related to the layout or not? Do they test on an EVM or their own board? Can they check it on an EVM?

  • 0 in reply to Wang5577
    TI__Expert 7395 points

    Hi Wang-san,

    Customer comment is below,

    ----------------------------------------------

    About your question,I would debug and show the test picture to you.
    1.can we stop or stuck the motor and check current waveform?
    When the motor spinning,I was stopped it and check current waveform,there have nothing be changed.
    TOFF 1,FULL-STP


    2.Can we change TOFF setting to 0 and HiZ to see the ripple change?
    I was changed toff pin to 0,and check the current ripple,but the ripple current have no changed.
    TOFF 0,FULL-STEP

    TOFF 0,1/4 STEP

    TOFF 0,1/8 STEP

    3.What is the micro-stepping setting?
    it was be full-step.And I also test others mode.and when worked at 1/8 step,current ripple is same table likely,but it is also not be ripple(toff 1)=11+2%*630=23mA
    TOFF 1,FULL-STEP

    TOFF 1,1/4 STEP

    TOFF 1,1/8 STEP

    4.Do they test on an EVM or their own board?
    We test at our own board,and we have no Environment of EVM.

    ----------------------------------------------

    Thanks 

    Muk

  • 0 in reply to Yusuke Mukuno
    TI__Guru 55655 points

    Mukuno-san,

    We are still investigating this and will reply within business day today.

  • 0 in reply to Ryan Kehr
    TI__Guru 56650 points

    Mukuno-san,

    I replied to the customer by email yesterday night. It seems they have to the early sample without final trim. Since it converts to offline discussion, let me close this e2e thread.

  • 0 in reply to Wang5577
    TI__Expert 7395 points

    Thanks Wang-san!