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DRV8711 Unclearable Fault

Nathan Smith
Intellectual 620 points
Other Parts Discussed in Thread: BOOST-DRV8711, DRV8711

I have been using a BOOST-DRV8711 module in conjunction with an MCU development board to drive a motor. I have been using this setup for several days. Yesterday, the BOOST-DRV8711 asserted nFAULT and I have been unable to clear it. When I try to communicate with the chip, the SDATO pin is always high and no data comes from it.

With the module disconnected from the MCU and motor, supplied with 27V on VM and 3.3V on 3.3, the module draws 35mA of current regardless of the state of nSLEEP or RESET.

The FETs are heating up, with Q4 being the hottest.

I pulled a new module out of the box this morning (it has never been connected to a motor) and it does the same thing, but draws 60mA.

The last thing I was doing when the MCU and motor were connected was changing the frequency of the STEP signal. Can a high-frequency step signal damage the module? I know my test setup seems to be the likely culprit because multiple boards exhibit the same behavior, but I cannot detect what is wrong. I feel like I'm missing something simple. What could it be?

  • 0
    TI__Mastermind 21305 points

    Hi Nathan,

    A high frequency signal shouldn't be a problem. The hot FET is very concerning. It is also strange that a fresh board exhibits the same behavior (does the same FET heat up?). The DRV8711 should be drawing about 20mA in STANDBY mode and 65uA in SLEEP mode.

    Can you give some more details about how you have the BoosterPack setup?

    • Which MCU? How is it connected to the BoosterPack?
    • What type of power supply  (battery, wall wart, bench)?
    • What kind of motor (datasheet) and what current are you driving to the motor?
  • 0 in reply to Nicholas Oborny
    Intellectual 620 points

    Yes, the Q4 is the hottest of the four on both boards. It's a gradient. If Q4 is 84F, then Q3 is 80F, Q2 is 76F, and Q1 is 72F.

    MCU is:

    connected with jumpers.

    DRV8711 is powered by two bench-top power supplies (one for 27V, one for 3.3V).

    Current limit set in TORQUE register is 300mA.

    Motor is Powermax II M22

    www.kollmorgen.com/.../powermax-m-and-p-series

  • 0 in reply to Nathan Smith
    Intellectual 620 points
    The output on V5 is only 2.6V and VINT is 1.2V.
  • 0 in reply to Nathan Smith
    TI__Mastermind 21305 points

    Nathan,

    Do both boards show the same voltages on V5 and VINT? This suggests that the DRV8711 has been damaged. Can you see that the DRV8711 is heating up itself?

    I am quite unsure how you would be damaging the IC though, especially the regulators if you are operating at 27V and only driving 300mA to the motor. The board is rated up to 50V on the power input.

    Can you take a scope capture of the power supply as it is applied and removed? Is there any under or overshoot?

  • 0 in reply to Nicholas Oborny
    Intellectual 620 points

    27V turn-on

    27V turn-off

    3.3V turn-off

    3.3V turn-on

    Yes, I believe the DRV8711 is heating up, too. With the FETs at 90F, the DRV8711 is at 100F.

  • 0 in reply to Nathan Smith
    TI__Mastermind 21305 points

    Hi Nathan,

    I don't see anything out of the ordinary. Can you check the regulator voltages on the other board?

    Are both the FET's and DRV87011 heating up or is the heat from the DRV8711 simply raising the temperature of the MOSFETs. It may be a good idea to replace the MOSFET's and see if there is any improvements. After that you can try and replace the DRV8711 (you can order replacements through a sample request).