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.
Power dissipation in normal mode is low at 30 mW typical and the part can be placed in a standby (power-down) mode if it is not required to perform conversions. The AD7890 is fabricated in Analog Devices, Inc."s Linear Compatible CMOS (LC2MOS) process, a mixed technology process that combines precision bipolar circuits with low power CMOS logic. The part is available in a 24-lead, 0.3" wide, plastic or ceramic dual-in-line package or in a 24-lead small outline package (SOIC_W).
**Product Highlights**
1. Complete 12-Bit Data Acquisition System-on-a-Chip. The AD7890 is a complete monolithic ADC combining an 8-channel multiplexer, 12-bit ADC, 2.5 V reference, and a track/hold amplifier on a single chip.
2. Separate Access to Multiplexer and ADC. The AD7890 provides access to the output of the multiplexer allowing one antialiasing filter for 8 channels—a considerable savings over the 8 antialiasing filters required if the multiplexer is internally connected to the ADC.
3. High Speed Serial Interface. The part provides a high speed serial interface for easy connection to serial ports of microcontrollers and DSP processors.
