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AFE4300EVM Settling Time

David_
Prodigy 120 points

Other Parts Discussed in Thread: AFE4300EVM-PDK, AFE4300

Hello,

I'm doing measurements with the AFE4300EVM-PDK Evaulation Board. I've encountered the problem that when switching to a different impedance to be measured or changing the injection frequency, the AFE4300 takes a rather long time to settle on the new value. It kind of looks like a RC curve. For example for a change of 600mV it takes about 300ms, forcing me to pause between consecutive measurements. Is that a limitation of the internal hardware (op-amps? adc? eval-board?) or a fault on my side? 

David

  • 0
    TI__Guru 50036 points

    Hello David,

    The settling time is due to the RC filter at the output of the demodulation circuitry. This filter helps in improving the noise at the expense of the signal bandwidth.

    For the optimum settling time, it depends on the noise and the signal bandwidth target (frequency of change in the impedance value). This is set by the ADC data rate and the corner frequency of the RC filter at the output of the demodulation circuitry.

    Can you provide more details about your application? How frequently would you like to change the impedance or change the injection frequency and take the measurements? What is the impedance range and the accuracy you are targeting for?