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ADS8319 value range

Pascal Bazelli
Prodigy 20 points
Other Parts Discussed in Thread: ADS8319

Hi there

 

I'm working with an ADS8319 ADC. The attached picture shows the part of the scematic where the ADC is located. REFIN is a reference voltage of 4.096V. So it should be possible to sample values between 0V and 4.096V at the analog input pin, right? But if I go up to about 2V at the analog input pin, the ADC already shows me a value of 65536 on the SPI data line. Why can I only use half of the value range I want to see? Any ideas?

  • 0
    TI__Mastermind 38085 points

    Hi Pascal,

    Thanks to ckoose our SAR ADC ,Can you check your SPI timing? especially your SPI's clock polarity and phase, which can lead to this kind of result if everything else is correct.

    In addition,two things should be noticed too:

    1. Inverting analog signal input(-IN). Note this input has a limited range of ±0.1 V, and typically it is grounded at the
    input decoupling capacitor. Balanced input is good but your 1kohm on -IN Pin may be higher,you can check the voltage on this pin.

    2. It is recommended to stop the SCLK clock during a conversion, as the clock edges can couple with the internal analog circuit and can affect conversion results(mentioned on Page 22).   

    Best regards

    Dale.

  • 0 in reply to Dale Li
    Prodigy 20 points

    Hi Dale

    Thank you very much for your hint. Changing the clock phase on the microcontroller did the trick. It was set up for getting data on the rising edge of the clock but should be set up for getting the data on the falling edge. Now it works fine!

     

    Best regards

    Pascal

  • 0 in reply to Pascal Bazelli
    TI__Mastermind 38085 points

    Hi Pascal,

    Glad to hear your good news and Welcome to this forum if you have more questions in the future.

    Thanks to choose TI's SAR ADC.

    Best regards

    Dale