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DRV8871: DRV8871

Arafet Toubib
Prodigy 10 points
Part Number: DRV8871
Other Parts Discussed in Thread: , DRV8251A

Hello, I'm encountering an issue with the DRV8871 motor driver and would appreciate some insight. I've been testing it with a DC motor and experimenting with the current limitation by adjusting the Rlim value according to the formula provided in the datasheet: Ilim = 64/Rlim. I've tried various current limitation values ranging from 2A to 4A.

However, after several tests and manipulations, particularly at higher currents, the driver starts emitting a sound similar to that of birds and I've also noticed a ticking sound. Additionally, it heats up very quickly.

Has anyone else experienced similar issues or have any suggestions on how to address this problem?

Thank you in advance for your help!

  • 0
    TI__Expert 5415 points

    Hello Toubib,

    Are you using the DRV8871evm or are you using a custom PCB for these tests. I recommend trying the same experiments on an evm to rule out any layout issues. How quickly does it heat up? What are your control signals during that time (waveforms would be helpful)?

    Can you share a schematic of your board if it is not the EVM?

    Best,

    Keerthi 

  • 0 in reply to Keerthivasan Kumanan
    Prodigy 10 points

    Hello Keerthi,

    Thank you for your prompt response. I appreciate your suggestion. I am indeed using a custom PCB for these tests, not the EVM.

    I have prepared a document containing the schematic, along with the command wave signals and a temperature curve. During the tests, the temperature rises from 31°C to 72°C in approximately 10 seconds.

    I have attached the document for your review and further analysis.

    https://drive.google.com/file/d/1jcv6rEEcpEIcnmmarDmYyXMfOIlE9MnC/view?usp=sharing 

    Best regards, 

  • 0 in reply to Arafet Toubib
    TI__Expert 5415 points

    Hi Arafet, 

    I am unable to open the drive link. Can you share the analysis as a PDF.

    Best,

    Keerthi

  • 0 in reply to Keerthivasan Kumanan
    TI__Genius 17998 points

    I was able to pull the PDF from google drive and have directly embedded it below:

    DRV8871 Test Report.pdf

  • 0 in reply to Jacob Thompson
    TI__Genius 17998 points

    Hey Arafet, 

    What is the continuous current of the DC motor you're using as the load?  

    A rise from 31°C to ~75°C seems reasonable to me with a sufficient load such as 0.5A or 1A motor, this is not concerning for the motor driver and is well within operating range of 125°C.  From your plot it looks like the temperature will stabilize around 75C.  If the device isn't tripping OTP (Over Temperature Protection) after several minutes then thermally it is fine for that ambient temperature and load. 

    See our favorite app note, Best Practices for Board Layout of Motor Drivers for suggestions on your layout to improve thermals.  

    Arafet Toubib said:
    However, after several tests and manipulations, particularly at higher currents, the driver starts emitting a sound similar to that of birds and I've also noticed a ticking sound.

    What frequency are you PWM at?  Often 20kHz is recommended so that the noise is outside of the audible noise spectrum. 

    If this is a new design I recommend trying out the DRV8251A instead - 50V/4.1A, and several years newer so has various improvements.  You can order the https://www.ti.com/tool/DRV8251AEVM for just $50 to try it out next week, and the hardware header pins make it easy to use your own control signals on it (just remove the 0Ω resistors).  

    Best,

    Jacob

  • 0 in reply to Jacob Thompson
    Prodigy 10 points

    Hi Jacob,

    Thank you for your detailed response and recommendations.

    Regarding your question about the continuous current of the DC motor, it is approximately 0.7A. During testing, I applied regenerative braking to challenge the current limitation option on the driver.

    Regarding the PWM frequency, I used a frequency of 80kHz.

    I appreciate your suggestion to try out the DRV8251A. I'll explore this option further.

    Best regards,

    Arafet Toubib

  • 0 in reply to Arafet Toubib
    TI__Genius 17998 points

    Hey Arafet,

    The results you're seeing seem reasonably for a 0.7A continuous load.

    Sounds good! Let me know if there's anything else I can help with.

    Best,

    Jacob