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DRV8711: is BEMF pin optional?

Part Number: DRV8711

Hi all,

I try to run motor using the DRV8711 but have not got any success so far. When I enable the motor through SPI getting 0x04 fault error over status registers which is over-current protection error. I realised that the BEMF left open in schematics. Do you think it could be reason of getting this error? Or any idea how to debug the board for that specific problem?

Here my design parameters:

VM:24V Rsense:0.03 ohms MOSFET: BUK7M10-40E  Motor Current:0.8A/phase Motor Resistance 13 ohm/phase

Any help would be appreciated.

Thanks.

  • Hi Mert,

    The BEMF pin is not required. It is there for information and should have no effect on the fault.

    Have you changed to 30milliOhms for the sense resistor? Are the register settings the same as your last post?
    (0x0, 0xF13)
    (1, 0x137)
    (2, 0x04D)
    (3, 0x1FF)
    (4, 0x50A)
    (5, 0x900)
    (6, 0x555)
    (7, 0x000)

    Do you ever get a 0x02 fault? If not, please check the connections.

    If you do, please try setting the setting the OCPTH to 11.
  • Hi Rick,

    Yes I have changed sense resistor to the 30milliOhms and I am using the same setting as you stated above.

    I never get 0x02 fault always getting 0x04 fault. When I disable the motor it disappears after clearing status register and come back when the motor is enabled. Also from the power supply I can see that current level is not changing at all and staying at 0.01A where VM is 24V.

    What do you mean by connections? The schematic is already printed on PCB. I dont think there should be problem with connections. 

    Thanks,

  • Hi Mert,

    Could there be a problem with a solder bridge or a FET causing the overcurrent event. Would you please check the impedance of all four sets of FETs, comparing the A side with the B side?

    Once the fault is asserted, all outputs are disabled in the event of overcurrent. The power supply current should be small after the fault.