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ADS8684: .

Wiley Braun
Prodigy 15 points
Part Number: ADS8684

I'm looking for technical support on the part ADS8684: I'm trying to find the value of the hold capacitance within the module for an individual analog input channel and I cannot find it within the datasheet. 

Also, I'm curious to know if the Auxiliary Channel will have the exact schematic (disregarding the front-end analog signal conditioning) as the other analog input channels since there is an input capacitance value listed on the ADS8684 datasheet (75 pF). 

Thanks,

Wiley

  • 0
    TI__Mastermind 45285 points

    Hi Wiley,

    Since ADS8684 has an integrated Analog Front End (AFE) on each channel including a PGA, 2nd-order LPF and ADC driver, this AFE eliminates the need of designing front-end amplifier to drive internal ADC so that the designer doesn't need to consider carefully how to settle input signal on internal sample-and-hold capacitor(CSH) of ADC during limited acquisition time which is common for switching capacitor input structure SAR ADC. This is the reason why the value of CSH is not stated in the data sheet directly.

    For Auxiliary channel, there is no AFE, so the input capacitance is useful for the designer to design a front-end driving circuit to drive the ADC, this is the reason why the value of CSH is specified in the data sheet. The input capacitance should be same for other channels because of same multiplexer and ADC core.

    Can you please let me know why you care about the sample-and-hold capacitor on 8 input channels (AIN0-AIN7)?

    Regards,

    Dale