AD7999,pdf,datasheet (4-Channel, 8-Bit ADC with I2C Compatib)

　　The AAD7999 are 12-/10-/8-bit, low power, successive approximation ADCs with an I²C compatible interface. Each part operates from a single 2.7 V to 5.5 V power supply and features a 1 μs conversion time. The track-and-hold amplifier allows each part to handle input frequencies of up to 14 MHz, and a multiplexer allows taking samples from four channels.
The AD7999 normally remain in a shutdown state, powering up only for conversions. The conversion process is controlled by a command mode, during which each I²C read operation initiates a conversion and returns the result over the I²C bus.
When four channels are used as analog inputs, the reference for the part is taken from V_DD; this allows the widest dynamic input range to the ADC. Therefore, the analog input range to the ADC is 0 V to V_DD. An external reference, applied through the V_IN3/V_REF input, can also be used with this part.