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ADS114S08: Analog input pin absolute input current spec

Adam Daluga
Expert 6385 points
Part Number: ADS114S08

Hello.

Can you help me understand the spec from table 7.5 that states 2nA max on the analog input pins? We had a few of the adcs get damaged on our boards with just RTDs attached to the inputs so we are trying to determine what caused the failures.

Thanks,
Adam

  • 0
    TI__Guru** 113765 points

    Hi Adam,

    The absolute input current you are referring to relates to the maximum bias and leakage current of the device.  Where you see the largest leakage is when the input pin is near the ground at high temperatures.  This is demonstrated in the graphs shown in and around Figure 10 of the ADS114S08 datasheet.

    The previous statement relates strictly to normal operating conditions and does not apply if the device input exceeds the absolute maximum ratings shown in 7.1.  The absolute maximum can be exceeded if the input voltage exceeds AVDD + 0.3V, AVSS - 0.3V, or +/- 10mA through the input pins.  This over-voltage or over-current can happen from a large transient of from some external connection that accidentally exceeds the maximum input voltage.

    For protection, TVS diodes and input filter resistance can limit the adverse effects.  Can you send me a schematic?

    Best regards,

    Bob B