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DRV8876: Burned during testing

Danilo A.
Mastermind 28560 points
Part Number: DRV8876

Hi Team,

Our customer is using DRV8876 in their application but some burned during testing. According to our customer,

In the application, the DRV8876 chip is used to control a geared brushed motor. The resistance of the motor winding is 8.7 ohms, 29 volts is applied to the control board. The control board contains a microcontroller and two DRV8876 to control 2 motors. DRV8876 operates in PH/EN mode and is controlled by a microcontroller. The microcontroller receives current feedback and an nFAULT signal from both motor drivers. During the test, the motors were loaded only by the gearbox, with a current consumption of about 300 mA. Spontaneously, on some instances of PCBAs, one of the motor drivers burns out, and the same one of 2 on all burnt boards. Replacing the DRV8876 seems to solve the problem, but there is no guarantee that it will not burn out on a longer test. There is a successful experience with DRV8876 in a similar control board with another microcontroller, and this control board is already in mass production. In what direction to look for a problem? What could be the problem?

I have copies of schematic diagram, PCB layout and specifications of the motor which I send can offline.

Regards,

Danilo

  • 0
    TI__Mastermind 37683 points

    Hi Danilo,

    Please send me the design files to my email or private E2E message.

    Some questions for the customer:

    • Are you providing a PWM signal to the EN pin? If so, at what frequency and duty cycle.
    • Are there any faults reported in the nFAULT pin?
    • Are the ICs completely damaged?
      • Danilo A. said:
        There is a successful experience with DRV8876 in a similar control board with another microcontroller, and this control board is already in mass production
      • Was there any major difference between this production hardware and the one experiencing the IC damage?
  • 0 in reply to Pablo Armet
    TI__Mastermind 28560 points

    Hi Pablo,

    Here is the feedback of our customer.

    >> Are you providing a PWM signal to the EN pin? If so, at what frequency and duty cycle.
    Yes, I provide a PWM signal to the EN pin. It is a 20kHz frequency with a variable duty cycle from 10 to 90% depending on motor required speed and applied load.

    >> Are there any faults reported in the nFAULT pin?
    Currently, the nFAULT pin is connected to the MCU input pin but is not read and not used by firmware. during the Lab test nFAULT signal was observed by using oscilloscope. The chip is not reporting any fault.

    >>Are the ICs completely damaged?
    Yes, it has no output voltage but has a variable nFAULT signal (1 changed by 0 and etc.).

    >>Was there any major difference between this production hardware >>and the one experiencing the IC damage?
    Yes, the major changes are both MCU (and firmware) and PCB.

    Regards,

    Danilo

  • 0 in reply to Danilo A.
    TI__Mastermind 37683 points

    Hi Danilo,

    I got the schematic through private message. Please give me 24 hours to review it.

    By the way, next time if you have sensitive information you don't want to share in the public forum, you can post the question to the internal forum.

  • 0 in reply to Pablo Armet
    TI__Mastermind 37683 points

    Hi Danilo,

    I replied via private email. Since we will discussing the customer's design, i will close this thread and continue the discussion via private message.