ADC FAQ - In the analog Input specification of a differential ADC, what is the difference between Analog Input Voltage Range and Absolute Input Voltage?

Document created by jcolao Employee on Nov 13, 2017
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A differential ADC has two input pins, Ain+ and Ain-. The analog value that the ADC will acquire and convert is the difference between these two input pins(Ain+ and Ain-) which means Ain+ - Ain-. The voltage range of this difference between Ain+ and Ain- is specified in the ADC specification table as Analog Input Voltage Range. Meanwhile the input voltage on a single ADC input pin is limited with respect to ground for both Ain+ and Ain- pins. The actual voltage that can be connected to each Ain+ and Ain- is found in the Absolute Input Voltage specification. For a unipolar pseudo Differential input ADC, the absolute input voltage and analog input voltage are equal, but for unipolar differential input ADC, analog input voltage can swing from -Vref to +Vref but the absolute input voltage is from 0 to Vref.