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About the over-range error of ad7172-2

Hello,
We have a circuit board designed based on AD7172-2 for wide-range measurement.
According to the data sheet of AD7172-2,the output result of the ADC should be 0xFFFFFF when an over-range error occurs. 
But we can’t get this value in the test.
What could be the cause?
Thankyou!

  • Hi,

    Can you share the output value from ADC and the input voltage to the analog inputs?.

    Regards,

    Andrei

  • Hello,                                                                                                                                                                The reference voltage of AD7172-2 is 5V and the input voltage of CH0 to the analog inputs is 6.1V. Look at the following picture, it shows the actual output value of CH0 from ADC is 0xB581BB (Big-endian) not 0xFFFFFF.

              

    Meanwhile, the ADC_ERROR bit in the status register is not 1s. 

     

  • Hi 

    May I know what is your supply voltages AVDD1, AVDD2, AVSS? I was thinking that the ADC might be powered incorrectly if the supply voltage is 0.3V lower than your analog input voltage as the internal ESD diode might turn on. Please make sure that your setup is within the part's operating range or abs max ratings. 

    Thanks,

    Jellenie