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ADS114S08: ADS114S08 vs MAX31865

George Zhao
Intellectual 1635 points
Part Number: ADS114S08
Other Parts Discussed in Thread: , ADS1120

Hello guys,

I am wondering in RTD acquisition application, what advantages does ADS114S08 have over MAX31865?

Thanks!

  • 0
    TI__Guru**** 180931 points
    Hi George,

    The ADS114SO8 has up to 12 input channels, programmable data rate options, programmable gain options, it can run from a bi-polar supply. There are other differences as well, please let us know your key concerns and we'll address them for you.
  • 0 in reply to Tom Hendrick
    TI__Intellectual 1635 points
    Hi Tom,

    I wonder does ADS114S08 have input protection or if not how do we configure protection for it?
    Thanks!

    Regards
    George
  • 0 in reply to George Zhao
    TI__Guru** 113765 points

    Hi George,

    The only protection built into the ADS114S08 is the ESD protection which is primarily for handling and fabrication.  Input protection is a complex topic and the type of protection that is required depend on what you are trying to protect against.  As a starting point I would suggest looking over the information found in the ADS114S08 applications section in the datasheet.  You can also review the information and schematic in the ADS114S08EVM user's guide (http://www.ti.com/lit/pdf/sbau272).  Also take a look at the general topic of RTD measurements in the RTD applications note (http://www.ti.com/lit/an/sbaa275/sbaa275.pdf).

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    TI__Mastermind 23275 points
    Hi George,

    following some additional differences between MAX31865 and our solutions using a discrete ADC, such as ADS1120 or ADS114S08.

    - MAX31865 can only support a single RTD. Our ADCs support measurements of multiple RTDs with one device in a same size or smaller package. Your customer was specifically interested in measuring three RTDs in his next design.

    - MAX31865 is limited to a few data rate options. Our ADCs offer a wide range of different data rates that you can choose from.

    - Our ADCs offer overall better accuracy (INL, offset and gain error) than MAX31865. Means RTDs can be measured with less temperature error.

    - MAX31865 offers an interesting feature with the 50V protection. However we usually recommend to place RC filters in front of the ADC inputs. The filter resistor can then at the same time also serve as a means to protect the ADC from overvoltages by limiting the current into the ADC inputs. Additional protection in form of Schottky diodes and/or TVS diodes might still be required depending on the customer needs.

    - The integrated fault detection features of MAX31865 are certainly nice. But the most important faults such as open RTD wire can easily be detected with the features we offer in our ADCs as well. Your customer was actually interested in measuring the resistance of the RTD lead wires itself in order to determine if they are corroding or are about to lose contact. This will only be possible with our ADCs, but not with MAX31865.

    Regards,