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ADS1282: PGA Saturating before absolute input rating

Shashank Meti
Intellectual 1010 points
Other Parts Discussed in Thread: ADS1282Hi Chris,

According to datasheet of ADS1282, the absolute input ratings are for positive: Avdd - 1.25 V & for negative Avss+0.7 V. For the positive input supply, the ADC is saturating at Avdd - 1.25 V (2.5 - 1.25 = 1.25 - working as per datasheet) but for negative input supply the ADC is saturating at - 1.25, according to datasheet it should be Avss + 0.7 (-2.5 + 0.7 = -1.8 ).
Can you please explain why is this happening?

Thanks,
Shashank
  • 0
    TI__Mastermind 44680 points

    Hi Shashank,

    I split this question off into a new thread since it is a unique issue on it's own. However, if you wouldn't mind following up on your previous thread (ADS1282EVM-PDK: EVM setup with the default MMBO) and letting us know if that issue was resolved, we would really appreciate it!

    For this problem, where the PGA negative rail appears to be saturating at a voltage higher than AVSS+0.7V, I need to know the input voltage and the PGA gain that you are using... Mostly likely, the input is exceeding the "Full-scale input voltage", ±VREF/(2 × PGA), which results in a full-scale reading. Might this be what is happening in your setup?

    Best regards,
    Chris