The operation of the ADC is optimized by separating the reference voltage into two operating ranges: low-reference range and high-reference range. The reference voltage range must be programmed to match the applied reference voltage, such as 2.5 V or 4.096 V. The low-reference operating range is 0.5 V to 2.75 V, and the high-reference operating range is 1 V up to the AVDD1 – AVSS power supplies. For best performance where the ranges overlap, such as reference voltage = 2.5 V, use the low-reference range. Program the REF_RNG bit of the CONFIG1 register to the appropriate reference range to match the applied reference voltage. When the high-reference range is selected, the input range is internally forced to 1x.