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DRV8889-Q1: Audible Noise

JINWOO CHOI
Prodigy 10 points
Part Number: DRV8889-Q1


Hi Team.

I'm JInWoo Choi. We are using DRV8889 for Automotive Actuator Application.

This application be required to detect  stall  so we applied Smart Tune Ripple control decay mode.

In this control mode, Stepper motor have audible noise but we can not much have parameters to try changing in register. 

( Other current decay mode also worse noise response as well)

As reference,Our previous Application not included current control function(without decay mode), show very silent output performance.

I'm wondering what's factors causing noise when decay mode is applied.  

So I'm looking for any solution in Motor itself. BackEMF waveform and difference peak-value in each Phases are not good in my points.

(See the blew waveform)

Please recommend me any tips to reduce noise. If we modify motor performance.  Thanks.

 

Fig1. wave form: Silent motor 

Fig2. DRV889 waveforms(1/32 micro stepping)

Fig3.: Motor Back EMF

  • 0
    Genius 5040 points

    Hi Jinwoo,

    JINWOO CHOI said:
    Please recommend me any tips to reduce noise. If we modify motor performance.  Thanks.

    Looking at the noisy motor driving waveforms, the 1/deltaX = 21.7Khz and caused high ripple motor current, and compare to the silent motor waveform with 1/deltaX = 49.5Khz with lower ripple motor current.

    Why the noisy motor was driven with lower frequency PWM?

    Brian

  • 0 in reply to Brian Dang
    Prodigy 10 points

    Hi Brian.

    Step Pulse input frequency is same.(21.7Khz)

    Silent motor PWM frequency is 21.7Khz, ripple current is high but output frequency is constant because there are no current decay mode.

    DRV8889 also have same base output frequency as 21.7KHz but this frequency is alternated cause of auto decay function like (Toff, Ton is varies according to torque changes and not symmetrical back EMF)

    At current regulation, fast decay logic is run, noise comes out I thinks.

    So at Motor side view, how we made  backEMF shape to reduce noise(to avoid fast decay logic run).

    Thanks.

  • 0 in reply to JINWOO CHOI
    TI__Guru 55655 points

    Jinwoo,

    We have an app note specifically on this topic.

    https://www.ti.com/lit/an/slvaes8/slvaes8.pdf

    For ripple control mode, there all no "knobs" to turn unfortunately in this device.  The ripple current is not adjustable.  

    And you are correct, Toff will vary with the smart tune ripple control.

    If you absolutely need STALL, then there are not any options here.  If STALL is not an absolute requirement, then we can try some of the other modes.  

    Regards,

    Ryan