Electronic Design

DACs Simplify Factory Process Control Designs

Working in extreme temperatures or at high voltages in factory process control, distributed control, and smart transmitter applications can be tough for 4- to 20-mA current-mode transmitters and analog I/O systems. Yet four 12- to 16-bit single-channel digital-to-analog converters (DACs) from Analog Devices can make those jobs easier.

These DACs integrate user-programmable current-source or voltage output. This makes them attractive because it simplifies design and saves space. The DACs’ appeal also lies in the fact that they don’t need tedious calibration to operate at extreme temperatures. They consist of two pairs of 16- or 12-bit chips with an SPI-bus interface that differ in their output characteristics.

The 16-bit AD5422 and its pin-compatible 12-bit cousin, the AD5412, operate from a single 12- to 48-V supply or dual ±12- to ±24-V supplies. Their output configurations are software selectable from options of 5 V, 10 V, ±5 V, and ±10 V in voltage mode and 4 to 20 mA, 0 to 20 mA, and 0 to 24 mA in current mode. All of their output spans include an additional over-range setting.

The 16-bit AD5420 and 12-bit AD5410 operate in current-source mode only. With a single 12- to 60-V supply, their output configuration is software selectable from 4 to 20 mA, 0 to 20 mA, and 0 to 24 mA. Taking the AD5422 as a representative, the family achieves an accuracy level of 0.1% total unadjusted error (TUE) while operating in voltage or current mode.

The chips include a precision 5-ppm/°C internal reference and an overtemperature indicator. Internal fault detection circuitry provides hardware and software indication of opens or shorts in cable wiring or remotely located loads. To sense output voltage, it includes a buffered voltage output with force and sense capability that can compensate for series protection resistors and fieldwiring resistance.

An on-chip programmable precision output amplifier allows rail-to-rail output swing. Analog outputs can drive capacitive loads up to 1 µF and inductive loads up to 1 H. They come in 24-lead thin-shrink small-outline packages (TSSOPs) and 40-lead lead-frame chip-scale packages (LFCSPs).

Sample units are now available. Unit pricing in quantities of 1000 range from $3.35 to $4.95.

Analog Devices www.analog.com

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