A data-acquisition system on a chip

Multifunction data-acquisition systems have been around for a long time as stand-alone instruments, plug-in cards, cabled computer peripherals, and embedded in systems. Such systems are often designed with separate ADCs, DACs, and digital I/O devices. Many microcontrollers include ADCs and DACs, but that locks you into using that device. The AD5592R from Analog Devices combines all of these I/O functions, letting you use one chip to design measurement-and-control functions into systems.

A data-acquisition system on a chip

Programmable through its SPI bus interface, the AD5592R contains eight 12-bit, successive-approximation ADCs, eight 12-bit DACs, a 2.5-V voltage reference, and eight digital I/O ports. The AD5592R also contains an internal temperature sensor that can measure from -40°C to +105°C, the device’s operating range. Each of the AD5592R’s eight I/O pins is configurable as an ADC, DAC, or digital I/O channel. Therefore, your application is limited to those eight channels, but in any combination. Building a data-acquisition system means you just need to add input-signal conditioning, output drivers, power, and communications to a microprocessor or FPGA.

ADC throughput rate is 400 ksamples/s, so you must divide that rate by the number of analog-input channels used to get the maximum per-channel sample rate. Each conversion takes 2 µs to complete. When configured as a DAC, each channel can drive a load capacitance up to 2 nF in parallel with 1 kΩ. In digital I/O mode, each channel can be configured as a general-purpose digital I/O line for detecting digital sensors or driving devices such a s relays to power transistors. Each channel is also configurable for digital logic inputs or outputs. You can program the device’s multiplexer for any channel sequence.

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