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ADS8688: ADC current signal input

walid Hanniche
Prodigy 30 points
Part Number: ADS8688
Other Parts Discussed in Thread: TIDA-00307, TIDA-00493, TCA6408A

hello,

i am trying to use the ADS8688 to read analog current values from a current sensors of the following values (4 mA to 20 mA, and ±20 mA.)

in the datasheet it is mentioned that this device support current inputs without the need of an external circuit (section 9.2.2.1, page 55)

but after checking the boards (TIDA-00307 and TIDA-00493), i found that it has been used an external circuit (shunt resistor + OA)

so my question is. does the ADC actually support current inputs or not ?

Thanks in advance.

  • 0
    TI__Mastermind 35540 points

    Hello Walid,

    Welcome to E2E forum.

    The section 9.2.2.1 in page 55 of ADS8688 datasheet describes a reference design based on ADS8688 precision ADC(TIDU365), this section mentions that this reference design can measure voltage or current inputs including 4-20mA and 0-20mA, not the ADC. Look at the section 5.1.2 and schematic of TIDU365, when measure 4-20mA current input signal, the host controller will control the switches(TLP3123) by TCA6408A to turn on the 200ohm burden resistor on the input, converting the input current to 0-4V voltage signal to ADS8688 with a full-scale range of 5V. Please refer to below block diagram.

    ADS8688 is a precision 8-ch,16-bit ADC and only support unipolar or bipolar single-ended input voltage signal.

    Please let me know if you have more questions.

    Best regards

    Dale

  • 0 in reply to Dale Li
    Prodigy 30 points
    thank you for your answer.