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LMV721 input voltage noise

Wiky Liao
Intellectual 1550 points
Other Parts Discussed in Thread: LMV721, LMV721-N, LMV722-N

Hi all,

My customer try to use LMV721 to finish AFCI signal conditioning. Due to the input is small, input noise is an important parameter.

From the 1st page, we get that LMV721 input voltage noise is 9nV/sqrtHz @1kHz .But it's different from the graph! So which is correct? 

  • 0
    TI__Mastermind 49906 points

    Hello Wiky,

    There are currently two LMV721 - the original National LMV721-N, and the second source from TI, the LMV721. Duplicate devices from National got the -N suffix.

    The graph you are showing is from the TI version. The noise graph does look a little "lumpy".

    The original LMV721-N datasheet has a much smoother noise graph (Fig 14), and shows 8.5nV at 1kHz.

    I can only speak for the LMV721-N (National version), since I took the original noise data almost 15 years ago, and I am not familiar with the TI version.

    Regards,

  • 0 in reply to Paul Grohe
    TI__Guru*** 140026 points

    Wiky,

     

    9nV may be from simulation, from characterization samples, or just copied from LMV722-N data sheet.

    11nV came from a sample that may not be from original char samples.

    Not every device will have the same voltage. Some will be a little higher or lower.

     

    If noise is very important then use 11nV and consider that some samples may be higher.

  • 0 in reply to Paul Grohe
    TI__Intellectual 1550 points
    Hi Paul,

    Thanks for your information, I got it. And I have check to BU and it's a typographical error. Thanks!