The AD7984 is an 18-bit, successive approximation, analog-todigital converter (ADC) that operates from a single power supply, VDD. It contains a low power, high speed, 18-bit sampling ADC and a versatile serial interface port. On the CNV rising edge, the AD7984 samples the voltage difference between the IN+ and IN- pins. The voltages on these pins usually swing in opposite phases between 0 V and VREF. The reference voltage, REF, is applied externally and can be set independent of the supply voltage, VDD.