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Original question:

DRV8873: Open load detection in passive mode

DRV8873: nFAULT PIN STATUS DURING OPEN LOAD CONDITION

Ashish NAWANI
Intellectual 255 points
Part Number: DRV8873

Hi,

We have connected the motor at H-Bridge OUT1 and OUT2 and simulating the OL condition in Passive mode, but we are getting the nFAULT pin status low.

1. Why we are getting the nFAULT status low when the motor is connected?

2. We have followed the datasheet parameters for OL detection in passive mode.

Can you suggest the possible reason for nFAULT status low?

Regards

Ashish Nawani

  • 0
    TI__Mastermind 37683 points

    Hi Ashish,

    I have a few questions:

    1. Are you using the TI DRV8873EVM or your own board?
    2. Are you using the SPI or Hardware variant of the DRV8873?
    3. If you are using the SPI variant, can you provide the register values?
    4. If you are using the Hardware variant, can you provide a picture or schematic of how you configured the DRV?

  • 0 in reply to Pablo Armet
    Intellectual 255 points

    Hi Pablo,

    1. Are you using the TI DRV8873EVM or your own board? - We are using DRV8873S SPI Version device in our own designed board.
    2. Are you using the SPI or Hardware variant of the DRV8873? - SPI
    3. If you are using the SPI variant, can you provide the register values?
      1. IC1_CONFIG_DATA               0x0080u
        IC2_CONFIG_DATA               0x00ADu
        IC3_CONFIG_DATA               0x0030u
        IC4_CONFIG_DATA               0x0040u
    4. If you are using the Hardware variant, can you provide a picture or schematic of how you configured the DRV? - N.A

    Regards

    Ashish Nawani

    We are using DRV8873S SPI Version device on our own designed board.

  • 0 in reply to Ashish NAWANI
    TI__Mastermind 37683 points

    Hi Ashish,

    Thank for providing the information.

    Are you performing the OLD test directly after power-up of the device or after device is powered on?

  • 0 in reply to Pablo Armet
    Intellectual 255 points

    Hi Pablo,

    We are following the mentioned steps: - 

    1. Connect the motor at the output.
    2. Power ON the device.
    3. Providing 5V to disable and sleep pin.
    4. Running OLD test.
    5. Reading SPI registers as no OL detected.
    6. Reading fault PIN status as 1V using a multimeter.

    We are following the same steps as mentioned in the datasheet. We are reading the SPI registers at every 10ms.

    The SPI registers are providing the correct values, even the complementary bit for nfault pin status is showing correct value. 

    Just the voltage reading at nfault pin is 1V at no-fault condition. 

    Regards

    Ashish Nawani

  • 0 in reply to Ashish NAWANI
    TI__Mastermind 37683 points

    Hi Ashish,

    Are you able to provide your schematics and layout at least for the section with the driver and the output connectors? You can send it to me via private message if you don't wish to share it publicly.

    If you follow the procedures from the datasheet and no are not seeing the OL detected then the next step is to look at your hardware to see if there could be any issues there.