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Original question:

LM2903-Q1: negative input voltage, max current

LM2903-Q1: VI min voltage

Mike Yu
Intellectual 1830 points
Part Number: LM2903-Q1
Other Parts Discussed in Thread: LM2903

Hi Team,

The customer have the question about the VI min voltage.

The OP IN- will be -0.55V when IN is -26V, but the LM2903-Q1absolute maximum rating of VI min is -0.3V only, will this be a problem? Thank you.

Best regards,

Mike

  • +1
    TI__Guru 51456 points

    Hello Mike,

    Please see the LM2903 family application note, particularly sections 2.6 and 2.9:

     Application Design Guidelines for LM339, LM393, TL331 Family Comparators

    -0.55V is getting into risky territory. But  the large 100k resistor will limit the clamp current of the input. At 100k, you just will not get enough current through the substrate diode to cause issues. You should be okay with a 10k resistor (~55uA).

    You may wish to change to a BAT54 type Schottky diode, that will bring the reverse voltage around -0.25V, depending on the amount of current through the diode.