AD7891

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.

PRODUCT HIGHLIGHTS

1. The AD7891 is a complete monolithic 12-bit data acquisition system that combines an 8-channel multiplexer, 12-bit ADC, 2.5 V reference, and track/hold amplifier on a single chip.
2. The AD7891-2 features a conversion time of 1.6 ms and an acquisition time of 0.4 ms. This allows a sample rate of 500 kSPS when sampling one channel and 62.5 kSPS when channel hopping. These sample rates can be achieved using either a software or hardware convert start. The AD7891-1 has an acquisition time of 0.6 ms when using a hardware convert start and an acquisition time of 0.7 ms when using a software convert start. These acquisition times allow sample rates of 454.5 kSPS and 435 kSPS, respectively, for hardware and software convert start.
3. Each channel on the AD7891 has overvoltage protection. This means an overvoltage on an unselected channel does not affect the conversion on a selected channel. The AD7891-1 can withstand overvoltages of ±17 V.

APPLICATIONS

• Data Acquisition Systems
• Motor Control
• Mobile Communication Base Stations
• Instrumentation