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ADS8588H: About PGA offset

Tao_2199
Genius 5680 points
Part Number: ADS8588H
Other Parts Discussed in Thread: ADS1112

Hello,

Regarding to PGA offset on ADS8588H, my customer is asking some question.

According to datasheet(page7), the offset error is described following.


They regard the characteristics near input 0V(offset) as important item of

simultaneous sampling ADC.

 

 

(Question)

(1) Is this data is only error of PGA? Or is it total error of ADC?

If it is total error, do you have the data of only offset error of PGA?

(2) For example, input offset of ADS112 is ±4uV(typ) at Gain=1 to 128.

Could you please tell me why ADS8588H’s offset is so large comparing with ADS112's?

Are these offset data decided by the different applications target ?

(4) Could you please give advice or comment about remove offset?

For example, do we need to remove offset by microprocessor after ADC output?

 

Regards,

Tao2199

  • 0
    TI__Mastermind 37140 points

    Hello Tao,

    Thanks for your query on E2E.

    1. The specifications in this table is system performance, including PGA, ADC driver and so on. This parameter is important for customers to evaluate total error on the signal chain, also it has covered different gains with different input ranges.

    2. I can't find ADS112 ADC on website, also ADS1112's offset error is higher. Generally the offset error shown in the datasheet of many delta-sigma ADCs is input referred offset with or without calibration, which is different from SAR ADC. If comparing with other SAR ADCs, ADS8588H's offset is not high, also this number has covered all errors contributed by analog front-end including PGA etc.

    3. If this offset error is a concern for the customers, a system calibration can be done. There are a lot of resource about calibration on website, below is a material for your reference.

    www.ti.com/lit/an/spraad8a/spraad8a.pdf

    Thanks.

    Best regards

    Dale

  • 0
    Genius 5680 points

    Hello Dale、

     

    Thank you for reply.

    I have informed to my customer your answer.

     

    I have an additional question.

    They will use 0-10V as input .

    In this case, they have concern that characteristics near input 0V.

    (input 0-10V -> ADC(PGA) -10 - +10V )

    I think that basically there is no problem at unipolar input because ADC(PGA) input is bipolar.

    My understanding is correct?

    Could you please give advice or comment?

     

    Regards,

    Tao2199

  • 0 in reply to Tao_2199
    TI__Mastermind 37140 points

    Hello Tao2199,

    Definitely there is no problem for ADS8588H to receive and convert your unipolar analog signal (0~+10V), but you are not using ADC's full scale and dynamic range, so you will not be able to see all output code.

    Thanks&Regards

    Dale