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DRV8873H-Q1EVM: Fault Occured when Open Load Detection is Enabled

Part Number: DRV8873H-Q1EVM

Hello everyone,
I work on the DRV8873H-Q1EVM.

I use it to control this kind of DC Motors: http://www.dinamikrulman.com/upload/pdf/NMB_Brushmotor/SE24P.pdfI'm in full bridge of course, the operation mode can be PH/EN or PWM the same error occured.
One DC Motor connected to IN1 and IN2.

  • Hello,

    "One DC Motor connected to IN1 and IN2."
    DC motor should be on output side, right?
    Open load detection detects the output current during the power up. If you put the load at input side INx, open load detection circuit cannot detect any load on output.

  • Hello,

    Thanks for your reply, I just made a mistake right here.
    It's not connected to IN1 and IN2 but to OUT1 and OUT2.

    Best Regards,

    Jean-François Marchal
  • Jean-François Marchal,

    1. When the fault was occurred, does the nSLEEP pin high or low? If nSLEEP is high, would you check the nFault pin with nSLEEP low?
    2. Do you put any capacitor on OUTx? Or does the motor have any capacitance on the input terminal?
  • Thanks for your reply Wang Li,

    1. nSLEEP pin high before and after the fault occured.

    Enabled Open Load Detection:
    -> At Start: nSLEEP LOW / nFAULT HIGH
    -> Wake Enable / Output State Enable: nSLEEP HIGH / nFAULT HIGH
    -> Start Motor (PWM: IN1(0%) / IN2(0%)): nSLEEP HIGH / nFAULT HIGH
    -> Start Motor (PWM: IN1(25%) / IN2(0%)): nSLEEP HIGH / nFAULT LOW
    -> IPROPI1 and IPROPI2 stay at 0A while motor working


    Disabled Open Load Detection:
    -> At Start: nSLEEP LOW / nFAULT HIGH
    -> Wake Enable / Output State Enable: nSLEEP HIGH / nFAULT HIGH
    -> Start Motor (PWM: IN1(0%) / IN2(0%)): nSLEEP HIGH / nFAULT HIGH
    -> Start Motor (PWM: IN1(25%) / IN2(0%)): nSLEEP HIGH / nFAULT HIGH
    -> IPROPI1 and IPROPI2 stay at 0A while motor working


    Set nSLEEP from HIGH to LOW clear the fault: nFAULT LOW to HIGH


    2. Capacitor of 1nF on the input terminal
    -> Test without capacitor same error occured

    Best Regards,
    Jean-François

  • Jean-François,

    In datasheet 7.3.2.4.2 Open-Load Detection in Active Mode (OLA) section, the open load detects the voltage across the FET's body diode.
    1. What load do you put on the output? Resistor load or a motor? I want to know can the motor winding or inductor load current keep passing the FET's body diode?
    2. Would you take some waveforms to check SH1, SH2 and VM voltage? If we can check the load current and show it on same waveform as SH1, SH2 and VM, it can help us.
  • Jean-Francios,

    Since no update over ten days, I am going to close this thread. If you have any update, you can reopen it by putting update in this thread.