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DRV8312: Bootstrap diode of Phase B malfunctioned

Sewoong Kim
Prodigy 60 points
Part Number: DRV8312

I　had developed several actuator systems with DRV8312 successfully, But newly developed controller suddenly stopped during operation without high current  of dc-link or fault signals of DRV8312.

We measured forward voltage drop(FVD) of bootstrap diodes(between the GVDD_X pin and BST_X pin) of DRV8312. The FVD of phase B were around 1.2~1.4V. Others are around 0.589V. We externally connected the GVDD_B pin and BST_B pin using a schottky diode, and malfunctioned controllers came back to normal operation!

I like to ask you followings.

1. What are the failure conditions of the diodes. Especially, What failure mode increase the forward voltage drop?

2. We are going to externally connect the pins using diodes to fix the controllers Will DRV8312 be all right? I like to ask you to recommend me diodes or ckt.

Sincerely

  • 0
    TI__Guru** 114905 points
    Hi Sewoong,

    What is the value of the BST_x capacitor?
    What is the switching frequency?

    Please note section 8.3.2.1 of the datasheet. This section provides guidelines that can limit the inrush current on the internal bootstrap diodes.
  • 0 in reply to Rick Duncan
    Prodigy 60 points

    HI Rick,

    All  BST_X capacitor is 0.1uF, and The PWM frequency is 40 kHz.

    So I didn't think only phase B has higher inrush current compare with phase A & C. 

    The DRV8312 operates in cycle-by-cycle current limit modes, and I tried not only complementary control scheme but also 2-quadrant switching scheme.

    Even though the datasheet recommend latch mode for 2-Q switching , both of the PWM switching scheme works O.K with cycle-by-cycle current limit mode

    Really they were looks ok since some of them passed the tests such as full load test or temperature test, etc.

    But they suddenly stopped even the actuators run at  light load such as 10Hz,  2.5 degree amplitude sinusoidal rotation with no load.

    Thanks