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LMP91000 problem with RE-WE 700mV setup

Other Parts Discussed in Thread: LMP91000

Hi,

I have a problem with setting 700mV between RE - WE.

My settings are: Vsup=2.8V, Vref=Vsup, Internal zero=20%, Bias=24%, polarization positive.

The highest differential voltage I get was 560mV. The polarization voltage is critical in my application.

Please help me in solving this problem.

Best,

Dariusz

  • Dariusz,


    I'm moving this post to the Precision Amplifiers Forum. LMP91000 have been answered out of this forum lately.


    Joseph Wu
  • Hi Dariusz,

    It is not possible to get to exactly 700mV with that supply/reference voltage.

    Your reference voltage is 2.8V.

    Internal zero is 20%, or 560mV on WE.

    Bias is the percentage of reference on top of WE (24% max).

    560mV + (2.8V * 0.24) = 1.23V on RE

    1.23V - 0.56V = 672mV sensor bias

    700mV/672mV = 1.0417

    2.8V * 1.0417= 2.9167V

    You would need a supply (or ext reference) of 2.9167V to get 700mV between WE and RE.

    Regards,
  • Dear Paul,
    Thank you so much for your clear explanation and help.
    In my case I can't get higher sensor bias than 560mV. Nothing is changing when I am shifting bias from 22% to 24%. As I remember, at the beginning of my work, which was few months ago, I could get sensor bias similar to your calculation result. From this time IC was extensively tested in different conditions so maybe there could be a problem with chip.
    Ones again thank you for ideas and very fast answer.
    Regards,
    Dariusz