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DRV8701: Audible noise with PWM mode

NOBUO FUJIHARA
Genius 9355 points
Part Number: DRV8701

Hi Team,

My customer asked to improve audible noise when they use DRV8701P + PWM mode control.

At this phase I don't get further information.

Could you give some advice to improve the issue, which point should I focus in terms of

- control (slew rate, frequency), and 

- hardware (like recommended snubber point and parameter)?

Thanks and best regards,

  • 0
    TI__Expert 8985 points

    Hi Fujihaha-san,

    There can from one to two main points from where noise can originate from:

    • Mechanical
    • Electric

    Let's start with mechanical. Is the motor an older or previously utilized motor? BDC motors tend to break down with usage, causing the brushes to "brush" against the rest of the motor components. This "brushing" leads to friction, generating noise. Additionally, build quality along with motor cooling fans can generate noise. Magnets, out of balance rotors, and bearing/winding issues can lead to noise generation.

    • Please, verify the motor age, build quality. and try to operate using a newer motor.

    As for electric, noise can depend on voltage spikes, ringing, and frequency the human ear can hear. 16kHz is referred to a good frequency operate in to avoid noise.

    • What is the frequency/duty cycle the customer is operating at?

  • 0 in reply to Hector Hernandez Luque
    TI__Genius 9355 points

    Thanks Hector-san,

    I discussed with customer, and it's not caused by motor itself.

    Customer has not monitored signals of key node, so I will get back with updated measurement results.

    Best regards,