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LMP91200 configuration

Timothy Scott
Prodigy 70 points

Other Parts Discussed in Thread: LMP91200

I'm designing a circuit incorporating the LMP91200. I have used the development board alongside the spi0-4 board and discovered that default settings on the LMP91200 suit my purposes. If I only use the default settings on the LMP91200 and have no need for SPI control, will the LMP91200 work without anything connected? What do I do with the pins if they are not connected to anything?

I have the power supply at 3.3v and the Vref at the same voltage. If not requiring the RTD function is it Okay to leave this floating or does it need grounding?

  • 0
    TI__Genius 9655 points

    Hi Scott,

    in the default configuration the LMP91200 measures the pH only. So you are not able to measure the temperature wiht a RTD (pT100, pT1000).

    In your schamtic I see a resistance (R8) connected to the CAL pin, you can remove it is unuseful. Moreover you should measure the VOUT vs. VOCM, in this way you remove the offset contribution of the VCM buffer. If you prefer a single ended measurement (your schematic) you need to take in account the offset of VCM buffer.

    regarding the other pins:

    leave GUARD2, VCMHI and SDO (also VCOM in case of single ended measurement) floating,

    connect SDI and SCLK to GND

    connect CSB to VDD

    regards,

    Domenico