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input impedance/resistance of MAX11259, MAX11254 and ad7124-4

FormerMember
FormerMember
Category: Datasheet/Specs
Product Number: MAX11259, MAX11254 and ad7124-4

Hi, what is the analog input impedance/resistance of MAX11259, MAX11254 and ad7124-4? From all the 3 datasheet, there is no such info but only something related to analog (differential) input current. Is there any way to calculate from the analog input current? Thank you.

  • Hi  ,

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    For AD7124-4, we list the input current specification rather than specify the input impedance. The input impedance can be calculated from this input current specification. When buffer is enabled, the absolute input current is +/-1nA for low power mode, +/-1.2nA for mid power mode and +/-3.3nA for full power mode. With Gain > 1, the input buffers are automatically enabled. Thus, it can handle any significant source impedances which allows external filtering necessary in your application. When, un-buffered the absolute input current is +/-2.65uA/V. These values can be found in datasheet specification section.  

    Regards,

    Rod

  • FormerMember
    FormerMember on Nov 10, 2023 3:00 AM in reply to RAdante
    0

    Hi Rod, thank you for your reply. So how to calculate from input current to input impedance/resistance? What level of external voltage source should it be used in the calculation? Assume the resistor (e.g. bridge sensor resistor) between the external voltage source and the analog input pin is very small compared to the equivalent input impedance/resistance, is it?

  • Hi  ,

    Your input impedance will depend on you AIN voltage. Just take note that the AIN voltage still follows the datasheet values.

    With this, computation for your AIN voltage/Input Current will depend on whether the ADC is in buffered or unbuffered mode. 

    Thanks and regards,

    Rod

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