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DRV8809: (1) This device has issues with stepper motor current setting accuracy

Carlo Pallini
Prodigy 20 points
Part Number: DRV8809

The following note:

" (1) This device has issues with stepper motor current setting accuracy"

is written at page 38 of the " DRV8809/10 Combination Motor Drivers With DC-DC Converters" document.

Could someone, please, elaborate?

  • 0
    TI__Intellectual 990 points

    Hello Carlo,

    I forwarded the question to the appropriate expert. Please expect a response by next Wednesday.

    Best regards,

    Bill Chieng

  • 0
    TI__Intellectual 990 points

    Hello Carlo,

    I reached out to the internal team and they mentioned the device has issues with current regulations. More specifically, the current regulations can not maintain current accuracy during operation. With that said, the DRV8809, DRV8810 User's Guide (Rev. A) recommends the following configuration:

    Best regards,

    Bill Chieng

  • 0 in reply to Bill Chieng
    Prodigy 20 points

    Hi Bill,

    thank you for the prompt answer.

    You actually report what is already written in the datasheet and the user's guide.

    I ask you, once more, to elaborate. 

    For instance, wouldn't the above recommendation prevent completely micro-stepping ?

    Please note, the datasheet mentions the same problem on A(C) currents:

    Best regards,

    Carlo

  • 0 in reply to Carlo Pallini
    TI__Intellectual 990 points

    Hello Carlo,

    Unfortunately, the DRV8809/10 does not have much explanation as to why this behavior is observed. The only documented information about this issue is from what you found in those datasheets & user's guide, which recommends those register settings. Additionally, the DRV8809/10's datasheet only has typical values(no min or max) listed in the stepper motor drive current specifications:

    I reached out for additional details from the previous support group, they also mentioned that a past customer determined that
    "this device[DRV8809/10] cannot be used for stepping motor." More specifically, "current regulation cannot keep good accuracy while operation. Current regulation go[es] up or down" from the expected current settings. 

    Overall, unfortunately, there is not much explanation in the following footnote: "This device has issues with stepper motor current setting accuracy" aside from what has only been stated. Therefore, the footnote provides a warning about the stepper motor current setting inaccuracy. Micro-stepping will likely be inaccurate with the DRV8809/10, hence the recommendation to fix the setting to the maximum current threshold (1111'b).

    Best regards,
    Bill Chieng

  • 0 in reply to Bill Chieng
    Prodigy 20 points

    Hi Bill,

    thank you for the novel answer.

    I find very strange that TI experts suggest to avoid micro-stepping (and even more strange that a past customer suggested to not use it with stepper motors). We have used  the DRV8809, in our products, with micro-stepping, for  years now.

    I am puzzled.

    If the DRV8809 is not appropriate for micro-stepping, could you please recommend me an alternative product?

    Thank you again and best regards.

  • +1 in reply to Carlo Pallini
    TI__Intellectual 990 points

    Hello Carlo,

    Regarding my statement above, I apologize if I was not clear. Based on the user’s guide recommendation: “setting 1111” essentially prevents you from micro stepping as you are fixing the register value.

    The datasheet mentions “issues with stepper motor current setting accuracy”. From this each current setting may not be accurately control the current at the target as previously discussed above.

    With that said, the footnote provides a warning for users about an issue observed regarding stepper motor current setting for the device. So, regarding your statement:

    • We have used the DRV8809, in our products, with micro-stepping, for years now.

    From our side, it’s not recommended because of the DRV8809’s current setting accuracy issue, however as long as you understand that there is a potential risk (specifically the current setting accuracy) it is okay to utilize that function.

    For your latter question:

    We do not offer an alternative device for the drv8809 with the same combo motor driver (https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/1083064/drv8809-alternate-part). 

    Although, you if are looking for motor driver specific for micro stepping you can find them with this link: https://www.ti.com/motor-drivers/stepper-driver/overview.html

    Best regards,

    Bill Chieng

  • 0 in reply to Bill Chieng
    Prodigy 20 points

    Hi Bill,

    Thank you very much. I really appreciate your help.

    Best regards.