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ADS8588S: ADC and AFE recommendation

Suresh Chandra Mannava
Prodigy 130 points
Part Number: ADS8588S
Other Parts Discussed in Thread: ADS8686S, ADS125H01, ADS8688, PGA855, PGA849, INA851

Tool/software:

I am working on designing an ADC circuit with the following specifications:

  • Channels: 8 differential or 16 single-ended.
  • Input Range: ±200 mV to ±10 V.
  • Resolution: 16-bit or 24-bit.

Could you kindly point me to the appropriate application notes and reference schematics that would help in implementing such a design using TI components? I am particularly interested in achieving high accuracy and low noise across the specified input range.

Your guidance on suitable ADCs, signal conditioning, and front-end designs would be greatly appreciated.

Thank you for your support.

Chandra

  • 0
    TI__Guru**** 181061 points

    Hi Chandra,

    The ADS8688S would be a fine choice for your application.  The ADS8686S is a 16 channel, 16-bit device which may also be of interest to you.  These are both successive approximation register (SAR) converters.  We also have delta-sigma converters with resolution up to 24-bits if you can deal with slower acquisition speeds.  You can find application notes under the 'Technical documentation' tab in the product folders as well as application schematics under the 'Design and development' tabs - look under Hardware development' for the EVM Users Guide.  There are also reference designs like TIDA-01576 which you may find useful.

  • 0 in reply to Tom Hendrick
    Prodigy 130 points

    Hi Tom,

    Thank you for the suggestions and guidance.

    Could you kindly recommend a suitable sigma-delta converter for our application? Our input range is ±200 mV to ±10 V, and we are particularly interested in achieving high resolution and accuracy.

    Could you provide recommendations for a circuit to support a 200 mV full-scale input voltage while maintaining performance across the specified range?

    Looking forward to your insights.

    Regards,

    Chandra

  • 0 in reply to Suresh Chandra Mannava
    TI__Guru**** 181061 points

    Hi Chandra,

    For 24-bits, we have the ADS125H01 - it's only a single channel device though @ 40kSPS.  It has an internal PGA with gain up to 128 and needs an external bi-polar supply to handle the high voltage inputs.  Would adding a MUX work for you?  How fast do you need/want to sample the inputs?

  • 0 in reply to Tom Hendrick
    Prodigy 130 points

    Hi Tom,

    Thank you for your suggestion regarding the ADS125H01.

    Our customer is looking for an ADC solution with 8 differential or 16 single-ended channels. They are currently using the NI-9205 and are aiming to reduce the footprint by integrating their custom logic with the ADC. Their primary requirement is a sampling rate of 250 kS/s, which aligns with their current setup.

    I don’t believe muxing the inputs is a concern in this case. Each channel should support programmable input ranges of ±200 mV, ±1 V, ±5 V, and ±10 V. Handling a single-channel ADC with a MUX and various front-end configurations may be a viable solution, but I’d like to confirm this approach with the community.

    I appreciate any recommendations for ADCs or implementation strategies that would address these requirements effectively.

    Thank you for your support.

    Regards,
    Chandra

  • 0 in reply to Suresh Chandra Mannava
    TI__Guru**** 181061 points

    Hi Chandra,

    OK - the ADS125H01 will not hit the target sampling rate.  On that front, the 250 kS/s requirement is for all 8/16 channels at 250K (31.25/15.625 kS/s per channel) or all 8/16 channels at 250 kS/s per channel?

  • 0 in reply to Tom Hendrick
    Prodigy 130 points

    Hi Tom,

    As per NI9205 datasheet, It looks like 250 kS/s Aggregate. It is also using MUX

  • +1 in reply to Suresh Chandra Mannava
    TI__Guru**** 181061 points

    OK then, the ADS8588 or ADS8688 would be the best option we have at the moment.

  • 0 in reply to Tom Hendrick
    Prodigy 130 points

    Thanks Tom,

    Any reference circuits or pointers on analog front end for ±200 mV, ±1 V?

  • +1 in reply to Suresh Chandra Mannava
    TI__Guru**** 181061 points

    Hi Chandra,

    I would need to look into the MUX portfolio - those parts are not something I deal with on a regular basis.  You could use the PGA849 or possibly the PGA855 as a driver to the ADC inputs.

  • +1 in reply to Tom Hendrick
    TI__Mastermind 22242 points

    Hello Suresh, 

    If you would like to further explore the PGA849 or PGA855, I recommend leveraging the existing calculator on the PGA855 product page, linked here: https://www.ti.com/tool/download/PGA85X-INPUT-OUTPUT-RANGE-DESIGN-CALC; here is a good overview document: PGA855 and PGA849 Product Overview (Rev. A)

    It will help you translate input range to an acceptable output range for the ADC while taking into account the requirements for common-mode and supply voltages. 

    Looking at your original question, seems like the following document will be helpful, specifically Architecture 6: PLC Analog Input Front-End Architectures

    The INA851 is the instrumentation amplifier version of the PGA855. If you would like the choice of gains 0.125, 0.25, 0.5, 1, 2, 4, 8, 16 - I recommend PGA855; for all other gains, I recommend implementing the INA851 with a gain setting resistor (RG). 

    If you have more questions regarding the PGA849 (single-ended output) or PGA855 (differential output), please start a new thread and reference this existing thread. 

    All the best,
    Carolina