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ULN2003A: Negative voltage of output

Hirotaka Inoue
Intellectual 2980 points

Part Number: ULN2003A

Hello support member,

Negative voltage spike is happen on ULN2003A output at turmimg off.

How much voltage level and term is acceptable for this negative voltage spike?

Regards, Hirotaka Inoue 

  • 0
    TI__Genius 10855 points
    Hi Hirotaka Inoue,

    Can you provide more information about the negative voltage spike? The internal flyback diode from collector to COM should be able to handle any negative voltage transients. What type of load are you driving?

    You can also try adding external Schottky diodes on the output to prevent negative undershoots. As described on page 12 of the datasheet, "The collector-emitter diode is a parasitic structure and should not be used to conduct current".

    Let me know if you have any questions,
    Arthur Huang
  • 0 in reply to Alpha H
    TI__Intellectual 2980 points
    Hi Arthur Huang,

    Thanks for your suggestion.

    The load is inductive as relay.

    Datasheet don't show negative voltage of absolute maximum rating.
    If we use external diode from emitter to collector for negative voltage, does ULN200A allow negative voltage of external diode Vf (0.5V) ?

    Regards, H.Inoue
  • 0 in reply to Hirotaka Inoue
    TI__Genius 10855 points
    Hi H.Inoue,

    You are correct, the datasheet doesn't contain negative voltage rating. I'll ask my team and see if we can get an answer. Most of our low-side switches are rated to go around -0.3V absolute max.

    What negative voltage levels are you experiencing? As stated earlier, the internal flyback diode should be able to handle negative transients. If the transient current draw is an issue, resistors in series could also help.

    The external Schottky should be connected from the output to GND. The ULN2003 already has a built-in diode from emitter to collector for negative voltages.

    Thanks,
    Arthur
  • 0 in reply to Alpha H
    TI__Intellectual 2980 points
    Hi Arthur-san,

    Thanks for your answer.

    Regards, H.Inoue