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ADS1292 - How to bias IN3P and IN3N if they aren't going to be used?

Ernesto Gonzales
Prodigy 225 points
Other Parts Discussed in Thread: ADS1292, ADS1292R, ADS1291

Dear all,

I'm working on an application in which I will use only 5 electrodes ( 2 for IN1, 2 for IN2, and 1 from the RLD).

However, I'm not sure how to bias IN3P and IN3N if I'm not going to use them. Should I ground them or pull them up to VDD by means of a pull-up/pull-down resistor? or are there other uses of it? (I saw that you can time multiplex IN3 with IN2 or IN1, but it's probably not convenient in my case as I really need the EMI filters in the input).

Also, are these IN3 inputs included in all the ADS1292 versions? or only in the ADS1292R one? 

  • 0
    TI__Mastermind 38745 points
    Hey Ernesto,

    Unused analog inputs should be pulled up to AVDD. There is no need for a resistor either; you can connect them directly. The IN3 inputs will be included on the ADS1292. The ADS1291, ADS1292, and ADS1292R will all come in the same package/pinout. Only the ADS1292R is capable of outputting the respiration impedance measurement carrier signal with those pins in addition to their corollary measurement functionality.

    Regards,
    Brian Pisani