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LM397 absolute maximum spec for Vout?

Roman Manka1
Prodigy 40 points
Other Parts Discussed in Thread: TL331, LM397, LM339, LM393, LM393-N

looks like the spec sheet does not have this important information, It's open drain and I would expect it to be higher then Vs. Can someone confirm what it is ?

  • 0
    TI__Guru 50036 points

    Hello Roman,

    The LM397 is a single version of the LM339 and LM393 comparator family, and was designed to be a replacement for the TL331.

    However, the LM397 does have ESD protection on the inputs and outputs, but I need to confirm if these structures will allow the output to exceed the supply voltage (i.e. a 36V Zener clamp to GND versus a "diode" clamp to V+). I have submitted the question to the designers to confirm.

    My gut feel is yes, it will allow the output to swing above V+ due to the 30V output leakage spec in the table - but I want to confirm.

    Regards,

  • 0
    TI__Guru 50036 points

    Hello Roman,

    The output can be taken up to 30V above ground, regardless of the supply voltage.

    The LM397 has >30V zener-like ESD clamps to ground on all the pins, so the inputs can also go above the rails without damage (but is still an illegal condition).

    Regards,

  • 0 in reply to Paul Grohe
    Prodigy 40 points

    so there is a 30V zener to GND at the output or >30V, it was not that clear.

    I'm looking for low power comparator that can handle at least 36V on the open drain/collector output

    Thanks

  • 0 in reply to Roman Manka1
    TI__Guru 50036 points

    Hello Roman,

    Yes. There are clamps to ground on all the input and output pins.

    Again, I have pinged the designers/process people to get this info.

    The Abs Max is 30V, so the only guarantee would be that it would not clamp at 30V, but it may clamp at 31V, or 32V, or...

    I just cannot feel comfortable giving an "OK" for 6V over the Abs Max.

    If you need 36V, then use the original LM393-N dual version as these do NOT have ESD clamps and are spec'd to 36V.

    Regards,