The AD79861 is an 18-bit， 2 MSPS successive approximation， analog-to-digital converter （ADC）。 It contains a low power， high speed， 18-bit sampling ADC， an internal conversion clock， an internal reference （and buffer）， error correction circuits， and a versatile serial interface port. On the rising edge of CNV， the AD7986 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. It features a very high sampling rate turbo mode （TURBO = high） and a reduced power normal mode （TURBO = low） for low power applications where the power is scaled with the throughput. In normal mode （TURBO = low）， the SPI-compatible serial interface also features the ability， using the SDI input， to daisychain several ADCs on a single 3-wire bus and provide an optional busy indicator. It is compatible with 1.8 V， 2.5 V， and 2.7 V using the separate VIO supply. The AD7986 is available in a 20-lead LFCSP with operation specified from ?40°C to +85°C.