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DRV8323R: I think I found major defect on DRV8323RS.

David Hwang
Prodigy 60 points
Part Number: DRV8323R

Hi this is David!

I am currently developing motor driver board with ti's drv8323rs chip(btw, I love this chip xD)

Anyways, I am using 1x PWM mode and there's a problem with this.

Whenever I put ENABLE to high it goes back to the initial value which is 6x PWM mode.(which is normal operation)

The problem here I think here is that the hall sensor line goes directly into INLA, INHB, INLB and do something with 6x PWM mode(might short since hall sensor INHB, INLB can get high on the same time)

So the motor makes some quite a loud noise before I turn into 1x PWM mode through SPI.(sometimes so large amount of current go through even the battery BMS cut the power)..

is it a defect?

if not, how can I solve this problem

Thank you for your help

  • 0
    TI__Guru** 114905 points
    Hi David,

    Thank you for your comment. We are currently investigating this and should have a reply by Tuesday.

    You should not be experiencing a short because the high side and low side FETs are not allowed to turn on at the same time in 6x, 3x, or 1x PWM modes.

    While waiting, we do have a few questions.

    1) Can you provide more information about the noise?
    a) Does this happen every time the device is enabled, or sometimes?
    b) If sometimes, have you measured the halls to determine the hall position(s) that this occurs?
    c) How long do you wait between enabling the device and setting 1x PWM in the registers?

    2) Do you have a GPIO on the INLC pin to brake the motor? If you do, can you try setting INLC to low prior to enabling the DRV8323RS? Doing this would disable current flow through the motor until the DRV8323RS is enabled and 1x PWM mode is configured.
  • 0 in reply to Rick Duncan
    Prodigy 60 points

    Hi again. Thank you for your help.

    1. about the noise, it's from the motor and sounds like 'tuck'

    A. It happens most of the time when I enable the device. And so far, I think it's related to motor position.

    B. No I have not measured it but I know it happens on certain position(hall position)

    C. I wait more than 2ms.

    2. Yes I do have one. I will try it and let you know!

    thank you for your kind answer!

    Happy weekend!

  • 0 in reply to David Hwang
    TI__Guru** 114905 points
    Hi David,

    Thank you for trying our request. We will await your results.
  • 0 in reply to Rick Duncan
    Prodigy 60 points

    Hi again!

    I have tried what you said: turning brake line(INLC) low.

    But it seems it's not working. I tried to see the signal with oscilloscopes, but I accidentally blew up the board...

    Anyways, while fixing the board, is there anything I can try? 

    Thank you for your help!

  • 0 in reply to Rick Duncan
    Prodigy 60 points
    I have done what you said on fully functioning board.
    And the result is same.

    Also I found some new one.

    After enabling the device and before configuring it to 1x mode(with debug mode), I spun the motor with my hand right, it spun like crazy.
    I guess hall sensor is acting like PWM to 6x mode. : I also tied INCL low here.

    Anyways. tieing INCL low is not working for me.. :(

    I look forward to hearing from you.
  • 0 in reply to David Hwang
    TI__Guru** 114905 points
    Hi David,

    Can you provide a schematic of the DRV8323RS connections to and from the motor and mcu?
    Do you plan to use the align and stop states available in the 1x PWM mode?
  • 0 in reply to Rick Duncan
    Prodigy 60 points

    Hi!

    I attached a schematic of DRV.

    I have not decided to whether to use or not the stop state but planning to manipulate hall sensor so DRV never gets 111 states (which is align state). 

    2867.Schematic.pdf

  • 0 in reply to David Hwang
    TI__Guru** 114905 points
    Hi David,

    Thank you for the schematic.

    As you noted the default is 6x. If INLA is 1, INHB is 1, and INLB is 0, you may have current flow from the B phase to the A phase when the device is enabled. To eliminate this possibility, two of the three phases should be off.

    From your schematic, phase C can be turned off if you know the state of the INHC pin on the board and set INLC to the same state.

    Phase A and B do not appear to be known. There are multiple methods to address this.

    If you plan to use the stop state, this would be very beneficial. Adding the ability to turn off the hall pullup voltage would allow entry into the stop state. By disabling the 3.3V, the internal pulldowns will set the INLA, INHB, and INLB low.

    Prior to enabling the device, use the stop state as described above and set the INHA to low to disable the all phases.

    Once enabled, the device can be set into 1x PWM mode and remains in the stop state since INHA=INLA=INHB=INLB=0.

    Finally, the pullup voltage can be turned on and the INHA can drive the PWM input.

    Please double check this procedure. This is based on the datasheet and has not been verified.
  • 0 in reply to Rick Duncan
    Prodigy 60 points

    Hi. Sorry for the late

    I have done what you have said, and it works just fine.

    Thank you for your help!