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!

Anonymous