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ADS7953: ADS values saturation and non linear ADC values

Karthik A
Prodigy 90 points
Part Number: ADS7953

Tool/software:

Hello.,

we are using linear potentiometer to vary the analog voltage and need to read respective ADC values but some times from our ADC output, if analog voltage from potentiometer is linear still we get non linear ADC output and sometimes if analog input varies ADC output will saturate to one value.

  • 0
    TI__Genius 15420 points

    HI Karthik,

    Can you share a schematic? What is the voltage connected to the potentiometer? What is the resistance of the potentiometer, and what voltage ranges correspond to the output at different resistances? Are you connecting directly to the ADC inputs? What sampling rate are you running the device at?

    Regards,
    Joel

  • 0 in reply to Joel Meraz
    Prodigy 90 points

    Hi Joel.,

    Thanks for reply.,

    From potentiometer output we are ensuring its from 0 - 5V linear voltage to the ADC input.

    ADC voltage varies from 0 - 5V with respect to that we are getting ADC output which is non-linear and sometimes saturates to one ADC value.

    Sampling rate : 50ms

    Graph pf voltage waveform is linear which is input to the ADC and ADC Output is no linear,

    Graph ref

    Reference sch

  • 0 in reply to Karthik A
    TI__Genius 15420 points

    Hi Karthik,

    Depending on how large the equivalent input RC values are, you might be seeing a signal settling error. Since I don't know what the input RC filter values or the potentiometer resistances are, I can't say for certain. That is usually the most common case, especially with high impedance inputs that are unbuffered.

    If you slow down the speed that you are sampling, does the error improve? If so, the input RC values might need some tuning to ensure that the signal is settling fast enough before the ADC finishes acquiring the signal. 

    Regards,
    Joel