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ADS114S08: Input Impedance

Part Number: ADS114S08

Hi Team,

May I ask the input impedance value of ADS114S08? I cannot find it in the datasheet.

My customer is considering to connect the input signal directly to ADS114S08 input, with internal PGA enabled, one concern here is that if this will affect accuracy? I suppose it should depend on ADS114S08 effective RIN.

Thanks.

Best Regards,

Livia

  • Hi Yazhu,

    Though the input impedance is not specified in the ADS114S08 datasheet, it is likely on the order of GΩs with the PGA enabled.

    However, the more important specification that is likely the input current, which is well-specified in the ADC datasheet. This tells you how much leakage current from the ADC will interact with the external conditioning circuitry and/or sensor impedance. The ADS114S08 has specifications for both absolute and differential input current, as well as the drift of each. This device also has input current plots that provide additional information about how the input current changes with respect to input signal under lots of different settings. Please see Figures 8 through 15.

    I can also tell you that the ADS114S08 input structure was optimized for low leakage, so you should be able to directly connect many sensors to the ADC inputs.

    -Bryan