• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 47 subscribers
  • Views 1503 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADS8684: Does ADS8684 support differential input?

wang jingang
Intellectual 320 points

Part Number: ADS8684
Other Parts Discussed in Thread: INA828, INA149

Hello,

1：does ADS8684 support differential input?If not, please help recommend ADC that can support differential input, thank you!

  • 0
    TI__Guru 50265 points
    Hello Jingang,
    Welcome to E2E forum.
    ADS8684 is a single-ended input ADC and can not support differential input signal. The voltage on AIN_nGND will have to be limited between -0.1V to +0.1V for specified specs, please refer to 7.5 Electrical Characteristics in page 7 of datasheet, also the maximum voltage on these AIN_nGND pins is -0.3V~+0.3V, see Absolute Maximum Ratings table in datasheet. Can you please let me know below information for a better recommendation?
    1. How many total channels do you need? is 8-channel enough or you need more?
    2. What's the highest voltage of your analog signal(peak-peak)? what's your common mode voltage for your signal?
    3. What's the sampling rate you want?
    4. Is 16-bit ADC enough?


    Thanks and regards
    Dale
  • 0 in reply to Dale Li
    Intellectual 320 points
    1：4Channels
    2：Input Range(Max)(V) 10.24 ，Input Range(Min) -10.24 ，Analog Voltage AVDD(Min)(V) 4.75 ，Analog Voltage AVDD(Max)(V)5.25 ，
    Digital Supply(Min)(V) 1.65 ，Digital Supply(Max)(V) 5.25
    3：Sample Rate(Max)(kSPS) <500
    4:16-bit
  • 0 in reply to wang jingang
    TI__Guru 50265 points

    Hello Jingang,

    Your information for No.2 is still not clear for me.

    • Your signal could be +/-10.24V for single-ended(SE) input, this is a SE bipolar input signal. ADS8684 can be used to convert this kind of analog signal directly to digital code.
    • Your signal could be +/-10.24V or lower for differential input, but definitely it should have a common-mode voltage which could be lower or much higher, this will determine what kind of front-end device is needed to handle this common-mode voltage. This was why I asked. For this kind of input signal, an Amplifier, Instrument Amplifier or Difference Amplifier is needed to convert your differential signal to a single-ended for ADS8684, there is a cookbook (sbaa247) to introduce this solution(the ADC in this cookbook can be replaced with ADS8684), also depending on your common-mode voltage level, INA828 or INA149 can be used, these cookbooks will come soon on TI website.         http://www.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=sbaa247&fileType=pdf

    Below block diagram shows one left example for SE signal and another right example for differential signal.

    Thanks&regards

    Dale