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ULQ2003A-Q1: ULQ200xx-Q1 Reverse Polarity

Julio Apps
Expert 3665 points
Part Number: ULQ2003A-Q1

Team,

How will the ULQ200xx-Q1 IC handle a reverse polarity condition between GND and the OUTx pin? Will this damage the GPIO from the MCU connected to the INx pin due to conduction of the diode between the collector and base of the transistor.

Julio

  • 0
    TI__Genius 10855 points
    Hi Julio,

    Reverse polarity conditions between Output and Emitter will damage the part or potentially damage the GPIO input. The body diodes within the device are usually reverse biased during normal operation and turn-on during inductive transient events. However, if the polarity is reversed, these diodes will activate. The ULQ200xx-Q1 can only handle around -0.3V before the diodes become biased.

    Thanks,
    Arthur Huang
  • 0 in reply to Alpha H
    TI__Expert 3665 points
    Arthur,

    Thank you for the detailed response. How would you recommend we protect the GPIO? A resistor at the gate to limit the current or maybe a diode to block during this condition.

    Thanks ,

    Julio
  • 0 in reply to Julio Apps
    TI__Genius 10855 points

    Hi Julio,

    You could try placing a diode at the output of the emitter (GND) to prevent reverse current during reverse polarity conditions. What voltage range is this reverse polarity condition at? Be careful, the body diodes are not intended to handle high power reverse current, the device can be potentially damaged if the diodes are biased in a high power reverse polarity condition. 

    Thanks,

    Arthur Huang

  • 0 in reply to Alpha H
    TI__Expert 3665 points

    Hi Arthur,

    This is Automotive off battery so  12-24V. I see, placing a diode between emitter (PIN E) and ground will have to block quickly so the reverse current does not increase to a level that damages the body diode of the transistor. 

    What is the ground at the bottom of the emitter of the transisto drawn in the block diagram belowr? I dont see that brought out to a pin. If this is still ground, current will flow through the base emitter diode into the GPIO regardless of having a diode between E and GND. Is that really ground or is it just floating?

  • 0 in reply to Julio Apps
    TI__Genius 10855 points
    Hi Julio,

    You are correct, it isn't real GND but more like an "internal GND". It will act as GND when the Emitter is connected to ground.

    Thanks,
    Arthur