The AD7891 is an 8-channel， 12-bit data acquisition system with a choice of either parallel or serial interface structure. 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 interface. The part operates from a single 5 V supply and accepts a variety of analog input ranges across two models， the AD7891-1 （±5 V and ±10 V） and the AD7891-2 （0 V to +2.5 V， 0 V to +5 V， and ±2.5 V）。 The AD7891 provides the option of either a parallel or serial interface structure determined by the MODE pin. The part has standard control inputs and fast data access times for both the serial and parallel interfaces， ensuring easy interfacing to modern microprocessors， microcontrollers， and digital signal processors. In addition to the traditional dc accuracy specifications， such as linearity， full-scale and offset errors， the part is also specified for dynamic performance parameters， including harmonic distortion and signal-to-noise ratio. Power dissipation in normal mode is 82 mW typical; in the standby mode， this is reduced to 75 mW typ. The part is available in a 44-terminal MQFP and a 44-lead PLCC.