Differential conversion feeds the two input channels to a differential amplifier with an optional gain stage. The output from the amplifier is then fed to the conversion logic, as shown in the Figure 1(B). Voltage differences from -VREF to +VREF therefore results in discrete output values from –512 to +511. The digital output is represented in 2’s complement form. Even when measuring negative voltage differences, the voltages applied to the input channels themselves must stay between GND and AVCC.
Voltage differences smaller than -VREF will return the minimum value (-512 using 10- bit ADC), and voltage differences greater than +VREF will return the maximum value (512 using 10-bit ADC).