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LMH6518: What's the cause of the offset drift in LMH6518

Patrick Zeng
Intellectual 1090 points
Part Number: LMH6518

Hi team,

  My customer has adopted LMH6518 in their end product. After running in the market for 5 months, one of the product was reperted abnormal behavior. Customerr found that LMH6518 has a huge offset change (up to 80mV)， while it's supposed to be much lower. It happens only after long time operation. 

  Customer is wondering what might be the cause for such a big offset drift (permanent drift)? It's related to heat or degradation? Thanks ahead for relying.

Reagrds,

Patrick

  • 0
    TI__Genius 15975 points
    Hi Patrick,

    Some questions to better understand the issue:
    1. Do you know the gain setting they are operating the part at? It seems that LMH6518 part has worse offset at HG setting. Also, the maximum output offset rated for the part is +/-40mV.
    2. Is the offset same for all the gain settings or is it the worst for HG gain setting?
    3. Also, are they able to measure the right gain out of the part?
    4. Do you have a schematic of how the LMH6518 is used in their application?

    Best Regards,
    Rohit
  • 0 in reply to Rohit Bhat
    TI__Intellectual 1090 points

    Hi Rohit,

      Thanks for looking at the issue.

      Customer points out that it happens only for LG gain settings, while HG gain setting is all right.

      I'll have to ask for the schematic. Just generally asking, what may be the potential cause of it? Thanks.

    Regards,

    Patrick

  • 0 in reply to Patrick Zeng
    TI__Genius 15975 points

    Hi Patrick,

    It is strange that the offset voltage happens only for LG gain settings, and not for HG gain setting as the datasheet says otherwise. There could be a number of reasons for the potential cause including the common mode control circuit to the overvoltage clamping. It is difficult to pin-point the root cause unless a thorough analysis has been made. How many units has the customer seen the issue on?

    Best Regards,

    Rohit

  • 0 in reply to Rohit Bhat
    TI__Intellectual 1090 points

    Hi Rohit,

      I've got customer's schematic. Can I send you e-mails and discuss it off-line? Thanks!

    Regards,

    Patrick

  • 0 in reply to Patrick Zeng
    Prodigy 90 points

    Hello Patrick,

    We are planning to use LMH6518 in one of our design. If you have resolved the issue, can you explain it, briefly?

    Best Regards,

    Mustafa DURSUN