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ADS1147: Only Get a integer value

Andy Jin
Intellectual 370 points
Part Number: ADS1147

Tool/software:

Hi expert, 

A strange thing happened,  

ADS1147 can only output an integer voltage value, for example, the actual voltage is 11.458MV, the ADC value is 2816 @PGA is 16 with SPS 20, the calculated voltage is 11.000mV, the internal reference voltage is 2.048V. After trying several times, it was the same result. What's wrong with this situation?

Thanks a lot!

Andy

  • 0
    TI__Mastermind 47091 points

    Hi Andy Jin,

    Can you measure back the reference voltage at the VREFOUT pin? Use a high precision DMM (6.5 digit or higher). It is unlikely the actual voltage at this pin is 2.048V, maybe it is 2.0479V, etc., which would change the voltage you are measuring to something like 10.9994mV

    You can also try calibrating the offset to see if that changes the results. See the OFC registers for more information

    Since the ADS1147 is only a 16-bit ADC and you are sampling very slowly, it is also likely that you will get very few code changes because the noise is <16-bit. So you should see a very steady code output from the ADC.

    -Bryan