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ADS1281: Input voltage range of the ADS1281

Masami Michino
Genius 5070 points
Part Number: ADS1281
Other Parts Discussed in Thread: ADS1287, ADS1262, ADS1220


Dear, All

Customers are considering using ADS1281 and ADS1287.
I would like to ask about the reference voltage and signal input voltage.

conditions:

AVDD = +2.5V, AVSS = -2.5V

VrefP = +2.048V, VrefN = 0.0V (GND)

AinP = +2.0V to -2.0V (single end input)
AinN = 0.0V (GND)

Please tell me whether ADS1281 and ADS1287 can perform correct AD conversion under the above conditions.

Thanks, Masami M.

  • 0
    TI__Mastermind 44550 points

    Hi Masami,

    The conditions you listed will work with the ADS1281; however, because the ADS1281 inputs go directly to the delta-sigma modulator the input source may need to be buffered (if it isn't already).

    For the ADS1287, there are a couple of issues to be aware of...
    - The reference voltage needs to be 2.5V (the 2.048V reference is outside of the ADS1287 data sheet specifications).
    - Additionally, because this part has an integrated PGA, the input range and output swing limitations of this PGA needs to be considered. In the case of the ADS1287, the input voltage should fall between +1.25V (AVDD - 1.25V) and - 1.5V (AVSS + 1V). With a +/- 2V single-ended inputs, this condition will not be met.

    May I ask what the intended application is for these devices? These parts are designed for low-power AC measurements and provide very good THD. If the customer is performing DC measurements and want the best noise performance, then I would recommend a different device, such as the ADS1262, which would be able to work under the above conditions and provide better DC resolution.

    Best regards,
    Chris

  • 0 in reply to Christopher Hall
    Genius 5070 points

    Hi, Chris-san,

    Thank you for your answer.
    I will respond to customers.
    Because their application is still in the research stage, they keep secret details.
    But since they are already using ADS1220, I think that they can use this instead of ADS1287.

    Thanks, Masami M.