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Original question:

ADS1013: reference voltage

ADS1013: reference Voltage question and difference between single-ended and Differential Mode

Frank Chien
Prodigy 40 points
Part Number: ADS1013
Other Parts Discussed in Thread: ADS1015, ADS1014

  There are some question below

  1. Assume our VDD is 5V ,The FS (Full-Scale Range)  is 5V or else (2.048V)?
  2. There is no change for FS   and LSB between single-ended / Differential Mode?
  3. single-ended is for positive? 0~+2.048V?
  4. Differential Mode is for neg/pos? -2.048~+2.048 (differential between AIN0、AIN1) 

           our schematic is below

  • 0
    TI__Expert 8140 points

    Hi Frank,

    Frank Chien said:
    Assume our VDD is 5V ,The FS (Full-Scale Range)  is 5V or else (2.048V)?

    The FSR of the ADS1013 is fixed at ±2.048 V.

    For ADS1014 and ADS1015, the full-scale range is configured by bits PGA[2:0] in the Config register and can be set to ±6.144 V, ±4.096 V, ±2.048 V, ±1.024 V, ±0.512 V, ±0.256 V.

    If you wanted to measure up to 5V, you would set the full-scale range of ADS1014/1015 to ±6.144 V, although the max output code would never be 7FFh since that would be the output code corresponding to +6.144V not +5V. 

    Frank Chien said:
    There is no change for FS   and LSB between single-ended / Differential Mode?

    No, but for single ended inputs, only the positive half of the FSR is available.

    Frank Chien said:
    single-ended is for positive? 0~+2.048V?

    Yes that is correct, this means that for single-ended inputs only the positive half of output codes is used. 

    Frank Chien said:
    Differential Mode is for neg/pos? -2.048~+2.048 (differential between AIN0、AIN1) 

    Yes. The negative half of the full-scale range corresponds to when the voltage at AINP is lower than the voltage at AINN. The absolute voltage with relation to GND at the input pins should not be negative, however. 

    Let me know if there are any other questions. 

    Best Regards,

    Angel

  • +1
    TI__Expert 8140 points

    Hi Frank,

    One more thing I forgot to point out. I took a look at the schematic, and I see that only AIN0 is connected and AIN1 is left floating.

    For ADS1015, you can have your input to AINX and use the mux settings to set AINN as GND.

    For ADS1013, AIN1/AINN should be tied to GND, otherwise you won't be able to get good readings. 

    Best Regards, 

    Angel

  • 0 in reply to Angel Rodriguez de San Miguel Bermudez
    Prodigy 40 points

    Thx Angel

    this is really help me, we have notice that floating pin , and we fixxed.