ad7991/ad7995/ad7999,4通道12/10/8位模数转换器I2C兼容接口引脚SOT-23

　　The AD7991/AD7995/AD7999 are 12-/10-/8-bit， low power， successive approximation ADCs with an I2 C®-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. Each AD7991/AD7995/AD7999 provides a 2-wire serial interface compatible with I2 C interfaces. The AD7991 and AD7995 come in two versions and each version has an individual I2 C address. This allows two of the same devices to be connected to the same I2 C bus. Both versions support standard， fast， and high speed I2 C interface modes. The AD7999 comes in one version. The AD7991/AD7995/AD7999 normally remain in a shutdown state， powering up only for conversions. The conversion process is controlled by a command mode， during which each I2 C read operation initiates a conversion and returns the result over the I 2 C bus. When four channels are used as analog inputs， the reference for the part is taken from VDD; this allows the widest dynamic input range to the ADC. Therefore， the analog input range to the ADC is 0 V to VDD. An external reference， applied through the VIN3/VREF input， can also be used with this part.