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LM2904: LM2904 Internal PN current tolerance

Steven Liu1
Expert 4505 points
Part Number: LM2904


Hi Team,

My customer used LM2904 for OBC design, but met one question as below. 

Under one special circumstance, there would be one 15mA current flow, last for at most 8ms going through below PN. Does it have the risk of damage?

Actually, customer did this test hundreds times, it still worked well. But as we can hardly find the current tolerance there, so need your help to confirm this. 

  • 0
    TI__Mastermind 30600 points
    Hi Steven,

    I'll need a little time to investigate this. Can you describe in detail the condition that causes the 15mA current flow? Are you providing an input voltage greater than VCC or something else?

    Thank you,
    Paul
  • 0 in reply to Paul Goedeke
    TI__Mastermind 30600 points
    Hi Steven,

    If you're pulling the input signal below ground, you're causing a protection diode which is between the input and ground to conduct. We recommend keeping the input current to less than 10mA for reliable operation and if this event is expected to happen frequently, then below 1mA. You can do this by putting an appropriately sized series resistor on the input pin.

    Best,
    Paul
  • 0 in reply to Paul Goedeke
    TI__Expert 4505 points

    Hi Paul, 

    Thanks for your reply. 

    According to your last comment, the current tolerance is ~10mA. Is that right ?

    Here is the circuit that the customer was using. the voltage between GND and HVDC- is ~120V. As there is 8K resistor between GND and HVDC-. So the current follow to the PN between LM2904 PIN4 and PIN5 is about 15ms, time last for 8ms at most. This is the real value. 

  • 0 in reply to Steven Liu1
    TI__Mastermind 30600 points
    Our guidance is 10mA max. If the design is able to tolerate an increase in resistance from 8k to 12k, you'll be able to limit the current to 10mA. However, if you expect this event to happen frequently, our advice is to limit current to 1mA.

    -Paul