The AD7989-1/AD7989-5 are 18-bit， successive approximation， analog-to-digital converters （ADCs） that operate from a single power supply， VDD. The AD7989-1/AD7989-5 contain a low power， high speed， 18-bit sampling ADC and a versatile serial interface port. On the CNV rising edge， the AD7989-1/AD7989-5 sample the voltage difference between the IN+ and IN? pins. The voltages on these pins typically swing in opposite phases between 0 V and VREF. The reference voltage， VREF， is applied externally and can be set independent of the supply voltage， VDD. Its power scales linearly with throughput. The AD7989-1/AD7989-5 are serial peripheral interface （SPI）- compatible， which features the ability， using the SDI/CS input， to daisy-chain several ADCs on a single 3-wire bus. The AD7989-1/AD7989-5 are compatible with 1.8 V， 2.5 V， 3 V， and 5 V logic， using the separate VIO supply. The AD7989-1/AD7989-5 are available in a 10-lead MSOP or a 10-lead LFCSP with operation specified from ?40°C to +85°C.