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Drv8432

ALbert Tello
Intellectual 725 points

We have some boards ( news) that one of the drv8432 are no working . I would like to know where is our mistake.

We use 4 per board , two are working and  two drv8432 are not working.

Symptoms in one boards

VDD=12 V,   PVDD = 24V,  M1=M2=M3=GND, ADJ = 100K to AGND

I would like to ask what can be the problem that FAULT goes low; OTW = (hight) and all output are set to   . The motor is working properly, and  not short in any point is found .

The motor is not moving , seems that drv8432  detects a short in some place, where can be .   

OUTA=OUTB=OUTC=OUTC=11V , and the controller is generating PWM signal ,  VCC1=5 V , VCC2 =3.3 V ara both OK , current consumption normal, (same when the boards is working properly )

Regards

Albert

What can be the problem  

  • 0
    TI__Guru** 114905 points

    Hi Albert,

    If you have two working and two not working on the same board, please take a look at the layout of the board.

    Is the layout of the 4 DRV8432 the same on the board?

    Are the two that are not working far away from the bulk capacitor? If so, consider adding a second bulk cap to power them.

    Can you provide a schematic and layout, pointing to the devices that work and the devices that do not work?

  • 0 in reply to Rick Duncan
    Intellectual 725 points

    Hi Rick

    Each drv8432 has its own bulk  cap and independent PVDD, you have the schematics from previous ticket.

    We have boards that are working fine. We are closing to production and we had  a preliminary run , 20 boards in total  and appears 4 boards has problem mentioned .

    1) Question PCB short: if the PCB is short in this can be the problem ? ,  Note: when we reset drv8432 and start the software both lines goes HIGH (OTW, FAULT).

    2) Questions <NO PCB SHORT> can be damaged drv8432  internally that can not step , Note: if we touch with a finger the heat sink is cold . Seems that is no passing current from the device to any place.

    Albert

  • 0 in reply to ALbert Tello
    TI__Guru** 114905 points

    Hi Albert,

    Since you have 16 boards working and 4 that do not, it could be something in the layout, fabrication, or assembly affecting operation. 

    Which devices do not work on the four boards? (U9, U13, U17 or U21)

    Using the clues available, please try to narrow it down.

    Another thought is the heat sink. How is it connected? It looks like a single heat sink is used? Is that correct?

    If so, is it possible the heat sink is not making good contact to the inner devices (U13 and U17)?

  • 0 in reply to Rick Duncan
    Intellectual 725 points

    Hi Rick

    I found the problem M1 line is controlled by dsPIC in all cases was touching a 3.3V as soon M1 was low the axis start working.

    In the 8412 EVB shows M1 is High  to work with stepper. Is any place that I can ready how to control stepper with M1 high ?,  or see PWM signals  ?

    Thank you very much Rick

    Albert

  • 0 in reply to ALbert Tello
    TI__Guru** 114905 points

    Hi Albert,

    I am glad to hear you found the problem.

    I

    ALbert Tello said:
    In the 8412 EVB shows M1 is High  to work with stepper. Is any place that I can ready how to control stepper with M1 high ?,  or see PWM signals  ?

    I am not sure what you want here. If you want to see the PWM signals after the DRV8432 CBC circuits, place a probe at the OUT_x pins of the DRV8432. You can compare them with the PWM_A inputs to observe the effect.