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Original question:

ADC128D818 input impedance of MUX off

ADC128D818: Input impedance

Bela Istvanfi
Prodigy 30 points
Part Number: ADC128D818

Ladies and Gentlemen,

I'm designing a driver circuit (HW) for ADC128D818.

In the datasheet, on page 8, there's a parameter: Ron. It is between 2k and 10k.

Is this the input impedance, what the driver circuit "sees", or is this the Ron resistance of the input multiplexer?

In case it belongs to the multiplexer (by the way, what can I do with this parameter?) so, what the input impedance is? What impedance has the driver circuit drive, for a correct measurement?

  • +1
    TI__Expert 8625 points

    Hi Bela,

    Thanks for your question. I'm not sure where in the circuit the Ron resistor is as that information is not available in the datasheet. The value may depend on temperature (TA = TJ = TMIN to TMAX). You may design the drive circuit assuming the max Ron. If using a voltage divider, consider the R2 sizing below:

    I hope that helps.

    Best regards,

    Samiha