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ADS8688: ADS8688+ADS8684 Daisy Chain

Naizeng Wang
Expert 5430 points
Part Number: ADS8688
Other Parts Discussed in Thread: ADS8684

Hi team,

As you can see in the Fig.73, if ADS8688 is in daisy-chain connection with ADS8684, for example, ADC1 is ADS8688 and ADC2 is ADS8684, can the system work in Manual CH n mode(Manual CH0 to Manual CH7)?  I think it can't work because  Manual CH4 to Manual CH7 is not valid for ADS8684. Right?

And I have another question. What's the function of Aux_in? I ask that because I found that customer didn't use this pin in their application. I want to know our design considerations about this pin while developing this chip. 

Br,

Naizeng

  • 0
    TI__Mastermind 45455 points

    Hi Naizeng,

    1. When the ADS8684 is used for the last ADC in the daisy chain, it will work and the last 16-bit data on CH 4-7 of last ADC can be ignored, see the timing below.

    2. The AUX channel can be used for different purposes, for example:

    •     Measure power supply.
    •     Low voltage signal 0-5V.
    •     High voltage signal with signal conditioning.

    Note that there is no internal AFE including PGA and ADC driver on this channel, a front-end amplifier may be needed to drive depending on the signal's characteristic.

    Best regards,

    Dale