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ADS1251 READ DATA PROBLEM

Other Parts Discussed in Thread: ADS1251

DEAR~

For ADS1251 Data reading problems,,I do not know why I read the data is unstable,,Please help me out as follows

Simple circuit as follows:


I use a logic analyzer to read data recorded as follows:
CH0:DOUT~~~CH1:SCLK~~~CH2:CLK~~~CH3:VCC=5V~~~CH4:VREF=4.096V~~~CH5:INPUT=1.000V
The first is to read to within 10 seconds of waveforms

Follow-up data is detailed analysis 0-4 seconds've read:

My program is as follows:

I do not know why the read data is incorrect,,You can help me?

  • Hi Sunny,

    Welcome to the the E2E Forums! I'm sorry for the delayed response, for some reason I didn't see your post until today.

    I haven't fully looked into your SPI communication yet, but I have a question and suggestion that I wanted to provide you with quickly...

    May I ask what sources you are using for your test voltage and your reference voltage?
    The ADC looks at the ratio "Vin/Vref" and computes an output code based on this ratio. If one or both of these voltage sources is noisy or unstable, the ADC results will be noisy and unstable. Therefore, I would first measure these voltages and see if they are stable.

    Additionally, if you short the ADC inputs, then you can rule out the input and reference noise sources as the cause. Try this test and see if the ADC noise performance is closer to expected.


    Best Regards,
    Chris

  • Dear Chris~

    Below is my reference to FIG.,,VCC and VREF of circuit is determined,,

    I do not know if there was an incorrect circuit...

  • Hi Sunny,

    I suspect that the reference voltage may not be stable. From the MAX6104 datasheet:

    Trying probing the reference voltage or applying another reference voltage from an external source and retake data to see if the results are more stable.

    Best Regards,
    Chris