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ADS1158: ADS1158 ADCINP & ADCINN Pin can floating ?

Kane Zhang
Intellectual 585 points
Part Number: ADS1158
Other Parts Discussed in Thread: OPA365

Dear Experts；

  Now wewant to use ADS1158 as a ADC for the breathing machine,  they don't use these pins: "ADCINP & ADCINN & MUXOUTP & MUXOUTN",  if we can floating these pins ? 

Do you have any better suggestion?

  • 0
    TI__Mastermind 44600 points

    Hi Kane,

    Yes, these pins can be floated. However, make sure that the BYPAS bit in the CONFIG0 register is set to 0 to internally connect the MUX output to the ADC input.

    Also, do keep in mind that the ADC inputs are switched-capacitor type and don't have the highest input impedance. Therefore, unless the input signal source is low-impedance (buffered) then we recommend buffering the input signal with an external amplifier, such as the OPA365 or OP320.

     

  • 0 in reply to Christopher Hall
    Intellectual 585 points
    Dear Chris，
    if i do not want to use these pins：ADCINP & ADCINN, MUXOUTP & MUXOUTN；how should i use ？
  • 0 in reply to Kane Zhang
    TI__Mastermind 44600 points

    Hi Kane,

    Referring to Figure 35...

    MUXOUT pins are outputs that are connected to you input signal (through the MUX connection). Therefore, I would leave these pins floating so as not to load your input signal.

    ADCIN pins are inputs and will not be connected to the ADC when BYPAS is set to zero. These pins may be left floating or connected to any voltage between AVSS and AVDD.

    In case you decide to use some signal conditioning circuitry in the future, it's never a bad idea to allow for component place holders between the MUXOUT and ADCIN pins (e.g. RC filters or amplifiers); however, do make sure that the MUXOUT pins are felt floating.