National Semiconductor’s Single-Wire 16-bit DAC for 4-to-20 Milliamp Loops Simplifies Smart Transmitter Design

National Semiconductor Corp. (NYSE:NSM) today introduced a 16-bit digital-to-analog converter (DAC)  featuring a single-wire interface and 4-to-20 mA current loop drive that simplifies the design of smart transmitters used in industrial two-wire sensor systems. The highly integrated DAC161P997  reduces component count and cost in factory and building automation control systems by enabling the use of a single isolation component to cross the isolation boundary. For sensing and detecting applications where galvanic isolation is not required, National’s DAC161P997 interfaces directly to a microcontroller.

The low-power DAC161P997 provides system designers an exceptional balance of accuracy, ease of use, performance and system cost. Its delta-sigma DAC offers 16-bit accuracy with a minimal temperature coefficient of 29 ppm and long-term output current drift of 90 ppm, while consuming less than 190 uA of supply current. The DAC161P997’s loop drive interfaces to a highway addressable remote transducer (HART) modulator, allowing injection of FSK-modulated digital data into the 4-to-20 mA current loop. The DAC operates over the -40 degrees C to 125 degrees C extended industrial temperature range.

Key Features and Benefits of the DAC161P997

    * Single-wire interface: enables higher system accuracy compared to discrete PWM implementations, and lower system cost compared to 4-wire SPI solution
    * Low power operation: 190 uA enables total system power consumption below 30 mW or 3.5 mA
    * User programmable start up conditions and data rate auto detect: allows system configuration for trade-off between update-rate vs. power consumption
    * Error detection and reporting: multiple error conditions detected automatically, providing higher system reliability

The DAC161P997 complements National’s innovative Sensor AFE Family in smart transmitter designs, including a wide variety of gas, temperature and pressure sensor applications.

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