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Nonlinear output of ADC AD7643

Question asked by harrycheung on Jun 22, 2013
Latest reply on Jul 16, 2013 by jcolao

Hi all,

 

I am using ADC AD7643 with an external reference of 2.5V and testing its 18-bit parallel mode. I calculate the voltage from the ADC digital output bits and compare it with the actual differential input between pin 43 and 39. There is significance difference between the two voltage. Yet the difference diminish at higher input voltage. What could be the problem?

 

 

 

 

Differential Input (mV)Voltage calculated from ADC output (mV)
49342.5
52691
571208
624315
672402
738519
900782
997918
11141073
12151197
13251314
14061392
15091507
15931601
17081702
18071867
18981912
20071995



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