NS公司的DAC161P997是用來發送工業標準4-20mA電流回路的模擬輸出電流的16位Sigma-Delta數模轉換器(DAC),提供16位精度,低溫度系數(29ppm/°C)的輸出電流以及極好的長期輸出電流漂移(90 ppmFS)性能,而功耗低于190uA,主要用于兩線4-20mA電流回路發送器,工業過程控制,激烈器控制,工廠自動化,建筑物自動化,精密儀表,數據采集系統和測試系統.本文介紹了DAC161P997主要特性, 方框圖,多種應用框圖以及應用案例電路圖,DAC161P997EVAL評估板電路圖和元件布局圖.

Single-Wire 16-bit DAC for 4-20mA Loops

The DAC161P997 is a 16- bit ΣΔ digital-to-analog converter (DAC) for transmitting an analog output current over an industry standard 4-20 mA current loop. It offers 16-bit accuracy with a low output current temperature coefficient (29ppm/°C) and excellent long-term output current drift (90 ppmFS) while consuming less than 190μA.

The data link to the DAC161P997 is a Single Wire Interface (SWIF) which allows sensor data to be transferred in digital format over an isolation boundary using a single isolation component. The DAC161P997’s digital input is compatible with standard isolation transformers and optocouplers. Error detection and handshaking features within the SWIF protocol ensure error free communication across the isolation boundary.

For applications where isolation is not required, the DAC161P997 interfaces directly to a microcontroller.

The loop drive of the DAC161P997 interfaces to a HART (Highway Addressable Remote Transducer) modulator, allowing injection of FSK modulated digital data into the 4-20mA current loop. This combination of specifications and features makes the DAC161P997 ideal for 2- and 4-wire industrial transmitters.

The DAC161P997 is available in a 16–lead LLP package and is specified over the extended industrial temperature range of -40°C to 105°C.

DAC161P997主要特性:

■ 16-bit linearity

■ Single-Wire Interface (SWIF), with handshake

■ Digital Data transmission (no loss of fidelity)

■ Pin Programmable Power-Up Condition

■ Self adjusting to input data rate

■ Loop error detection and reporting

■ Programmable output current error level

■ No external precision components

■ Simple interface to HART modulator

■ Small package: LLP-16 (4x4 mm, 0.5 mm pitch) 4.0 Key Specifications

■ Output Current TempCo 29 ppmFS/°C(max)

■ Long-Term Output Current Drift 90 ppmFS(typ)

■ INL +3.3/−2.1 μA(max)

■ Total Supply Current 190 μA(max)

DAC161P997應用:

• Two-wire, 4-20 mA current loop transmitter

• Industrial Process Control

• Actuator control

• Factory Automation

• Building Automation

• Precision Instruments

• Data Acquisition Systems

• Test Systems

圖1. DAC161P997方框圖

圖2. DAC161P997工業用4-20mA發送器框圖

圖3. DAC161P997回路供電的發送器框圖

圖4. DAC161P997自供電的發送器框圖

圖5. 變壓器耦合SWIF鏈接的DAC161P997發送器框圖

圖5. DAC161P997典型的SWIF鏈接框圖

圖6. 無雙向I/O的主鏈接框圖

圖7.采用光耦的SWIF鏈接框圖

圖8. DAC161P997應用案例電路圖

DAC161P997EVAL評估板

DAC161P997EVAL is the evaluation board for the DAC161P997 Single-Wire 16-bit DAC for 4-20mA Loops. This board will help the user evaluate the functionality and performance of the DAC161P997. It is also a demonstration tool for the DAC’s unique single wire interface (SWIF).

DAC161P997EVAL combined with SPIO4 Sensor AFE Digital Controller Board the user can easily build a 4-20mA remote industrial transmitter where the PC host emulates a process sensor.

圖9.DAC161P997EVAL評估板外形圖

圖10.DAC161P997EVAL完整的評估系統

圖11.DAC161P997EVAL評估板電路圖

圖12.DAC161P997EVAL評估板元件布局圖
詳情請見:
http://www.national.com/ds/DA/DAC161P997.pdf
和
http://www.national.com/assets/en/boards/DAC161P997_UserGuide.pdf