The AD7890 is an 8-channel 12-bit data acquisition system. The part contains an input multiplexer， an on-chip track/hold amplifier， a high speed 12-bit ADC， a 2.5 V reference， and a high speed， serial interface. The part operates from a single 5 V supply and accepts an analog input range of ±10 V （AD7890-10）， 0 V to 4.096 V （AD7890-4）， and 0 V to 2.5 V （AD7890-2）。 The multiplexer on the part is independently accessible. This allows the user to insert an antialiasing filter or signal conditioning， if required， between the multiplexer and the ADC. This means that one antialiasing filter can be used for all eight channels. Connection of an external capacitor allows the user to adjust the time given to the multiplexer settling to include any external delays in the filter or signal conditioning circuitry. Output data from the AD7890 is provided via a high speed bidirectional serial interface port. The part contains an on-chip control register， allowing control of channel selection， conversion start， and power-down via the serial port. Versatile， high speed logic ensures easy interfacing to serial ports on microcontrollers and digital signal processors. In addition to the traditional dc accuracy specifications such as linearity， full-scale， and offset errors， the AD7890 is also specified for dynamic performance parameters including harmonic distortion and signal-to-noise ratio.