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FAQ: How to convert the AD7124-4/AD7124-8 data output Code to equivalent analog input voltage?

As discussed in What is the data output coding format used in AD7124-4/AD7124-8?  the ADCs operate in unipolar or bipolar coding modes.

When unipolar mode is selected the ADC output code for any analog input voltage applied to the analog inputs can be calculated using the following formula as:

 

 

Code = (2^N × AIN x Gain)/VREF

·        where AIN is the applied differential input voltage

·        VREF is the reference applied to the ADC.

·        N = 24 (number of data output bits)

·        Gain is the PGA settings

 

Example: AIN = 1V, VREF=2.5V, PGA = 1. The equivalent code in unipolar mode is

Code = (2^N × AIN xGain)/VREF = (2^24 x 1V x 1)/2.5V = 6710886

When bipolar mode is selected the ADC output code for any analog input voltage applied to the analog inputs can be calculated using the following formula as:

 

 

Code = 2^ (N – 1) × [(AIN x Gain/VREF) + 1]

 

·        where AIN is the applied differential input voltage

·        VREF is the reference applied to the ADC.

·        N = 24 (number of data output bits)

·        Gain is the PGA settings

 

Example: AIN = 1V, VREF=2.5V, PGA=1. The equivalent code in bipolar mode is

Code = 2^ (N – 1) × [(AIN/VREF) + 1] = 2^ (24 – 1) × [(1V x 1/2.5V) + 1] = 11744051

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