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AFE4300 ADC channel switching settling time

ccent
Intellectual 340 points
Other Parts Discussed in Thread: AFE4300

When operating in IQ mode, the AFE4300 requires reading two separate demodulator channels using the same A/D. This requires constant switching of the signal source to the A/D using the on-board multiplexer. What is the required settling time after switching from the I to Q channel? How fast can the part be operated in IQ mode? I assume that switching the channel will require some settling due to the delta sigma converter and filter.

Thank you! 

  • 0
    TI__Mastermind 49956 points
    Hello Ccent,

    If we assume that the change in impedance is very slow & close to DC, switching from I & Q (&vice versa) for a single channel : the settling time will depend on the data rate of the ADC. But if you are switching between multiple BIA Channels : the settling time will depend on the filter time constant. Assume at least 12 time constants based on the R & C.

    Regarding how fast the part can operated in IQ mode, the answer will depend on the noise and 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.