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DRV8872: Issue with a motor integrates capacitor and varistor

Alvin Zheng
Intellectual 900 points
Part Number: DRV8872

DRV8872Q1 met issue in one automotive account.

Attached motor structure and parameter. 

All the test were run on EVM.

If set INx prior to VM, the motor can start-up and spin.

If set VM prior to INx, the nFault indicator LED lights on, waveform shows OCP seems to be triggered and auto-restart every 3ms.

Replaced current sensing resistor to 150mohm, 330mohm, 400mohm, 500mohm, 750mohm, 1ohm. The issue remains.

Considering the charging to capacitor leads to the OCP during start-up at high VM, current limitation should help to limit the start-up current and get the motor spin.

Wonder why the current regulation circuit seems does not effective in this case.

  • 0
    TI__Guru** 114905 points
    Hi Alvin,

    The sense resistor should be less than 400 mOhm for this motor. Any higher violates the ISEN absolute max of the 1V.

    Is it possible to reduce the 1uF capacitor. The OCP is probably caused by the capacitor.

    If you have a current probe, please zoom in to capture the current during each pulse. The current is exceeding 3.7A for ~1.5us. If you do not have a current probe, please zoom in to capture the sense resistor voltage. This can provide similar information.

    Also please provide the two output voltages.