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LMP91000: Need to reduce voltage/currented sensed at the electrode.

Part Number: LMP91000

So in the application of this device, I occasionally see the Vout levels go negative, which isn't necessarily a problem, however, my micro controller does not pick up these values (i.e. the values just read 5,4,3,2,1,0,0,0,0,0,0...... 0; instead of showing the negative values). Would the Internal 0 or the TIA gain have to be adjusted in order to shift the Vout levels upwards so that a sensing application that might normally have a low peak at -50 mV would have its low peak adjusted to 0 mV, along with all of the other values, respective of their original values, everything be shifted up.  Is this possible?

2 Replies

  • Alternatively, I wanted to add... Is there any way to allow my microcontroller to read negative values? I've heard something about voltage dividers and need some guidance implementing if that's the answer.
  • In reply to Justin Hathaway:

    Hi Justin,

    Sorry for the delay in the answer.

    Yes it is possible to adjust your output range in order to do not have negative peak. Possible solution are:

    1. Modify the VREF and/or the INT_Z configuration (REFCN - Reference Control Register - address 0x11) in order to increase your internal zero;
    2. Reduce the TIA_GAIN (TIACN - TIA Control Register - address 0x10), using one of the embedded resistance values, or using an external resistance.

    Please let me know if this replies to your question.

    Best regards,

    Carmine

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