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Original question:

DRV8711: DRV8711

DRV8711: several bits of STATUS register set in low temperature occasionally

Bruce li
Genius 5580 points
Part Number: DRV8711

Dear TI Experts,

My customer is testing DRV8711 in a outdoor controlling system. They tested 8pcs prototypes, everything works fine in room temperature.

However, when in low temperature(-20 degrees), there are several warning  register bit are set in 3 samples out of 8pcs  ( STDLAT /UVLO / BPDF bits of STATUS register ).

Gererally speaking, this will happen after 1~2 days continuous working, they can use host command to clear these bits and recover normal work, and after another 1~2 days, these bits will set again.

Could you kindly help to give some advices about this issue? Thanks a lot.

  • 0
    TI__Guru** 114905 points
    Hi Bruce,

    We have not heard of any problems of this nature. From the description, one probable scenario could be moisture build-up.
    Is it possible that humidity is causing the problem at low temperature?

    Does the time between failures vary?
    What is the humidity at -20 degrees?
    Is the board protected from humidity? (Conformal coating or potting)
    Were any steps performed on the boards after the bits were set (heating the boards, cleaning the boards, something else)?
  • 0 in reply to Rick Duncan
    Genius 5580 points
    Dear Rick,
    Thanks a lot for your timely support, I'll check with customer about these questions and reply you.
  • 0 in reply to Bruce li
    TI__Guru** 114905 points
    Hi Bruce,

    Have you heard back from the customer?
  • 0 in reply to Rick Duncan
    Genius 5580 points

    Dear Rick,
    Sorry for the late reply, customer has no protection from humidity on the test before, they will try the test later, they are busy on another project these days. I've got feedback later. You can close this thread if necessary.

  • 0 in reply to Bruce li
    TI__Guru** 114905 points
    Hi Bruce,

    Thank you for the update. We will close the thread. If you have additional information, please reply to this thread or select "Ask a related question".
  • 0 in reply to Rick Duncan
    Genius 5580 points
    Dear Rick,
    I visited customer yesterday, here is the detail for this case:


    1) Their PCBA is in sealed case so they don’t suppose the humidity is the problem
    2) They have 5pcs PCBA worked over 1 year at 0 degree, it will be set UVLO flag sometimes, this flag will not stop the driver output and the motor keep running, so it is acceptable
    3) They have 3pcs PCBA testing in -20 degree, at first, only UVLO flag was set just as 0 degree, after 2 months, BPDF and STDLAT flag started to be set occasionally, once these two flag is set, the motor stopped. Customer need to send command from MCU to clear related flag, then the motor recover to run again.

    Could you kindly help to suggest the possible reason for these two flag set in -20 degree?
    Is there any other devices can replace DRV8711, so I can ask customer to try it? Thanks a lot.
  • 0 in reply to Bruce li
    TI__Guru** 114905 points
    Hi Bruce,

    Let's focus on the BPDF first.

    Please refer to section 8.1.2 of the datasheet.

    Does the customer have the optional gate resistors installed on the low side?
    If not, please provide a layout of the low side FET connections from the DRV8711 to the FETs.
    What is the VM voltage?
    What is the motor current? Has the current increased at -20C versus 0C?
  • 0 in reply to Rick Duncan
    Genius 5580 points

    Dear Rick,

    Thanks a lot for your support, I'll check with customer.