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AD7797

Question asked by DinamicaS on Oct 7, 2010
Latest reply on Oct 8, 2010 by MMA

My question is focused on use of full scale register on AD7797.

I wrote on this register very different values, just for test, and after each of these changes I try to read the count digit value applying as input the same analog value equal to 17.5mV.

What I don’t understand is: why the output digit value is always the same? Of course during this test the analog input is the same BUT the full scale register is very different so I expected that sometimes the output digit is near the maximum value 0xFFFFFF and sometimes is smaller.

What I’m asking is to confirm me if my theory is wrong or it is correct but I’m doing not correct SPI operations and this is the reason why it doesn’t work.

 

Further, before use the AD7797 I worked with AD7714 and regarding this point it works fine, I mean that the analog input that is necessary to apply in order to have a digit code as 0xFFFFFF (maximum value) it depend on the voltage applyed during the calibration of full scale register phase as expected.

 

Thanks in advance for any suggestion.

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