Dual Sensor Measurement Using Single Current-Loop with FSK Modulation Reference Design
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Key Document


The TIDA-00483 reference design demonstrates a 4-20mA current loop subsystem capable of measuring the surrounding environment and communicating the temperature, humidity, and ambient light over the loop. The small footprint of the design contains all sensors, filters, and control circuitry to calculate and communicate the sensor data. The reference design is intended for process measurement applications in factory automation, field transmitters and building automation. The sensors, MCU and communication modules all run from the current loop power, requiring less than 3.5 mA.

  • Reduce cabling and installation cost by transmitting two variable parameters simultaneously on a 4-20mA current loop
  • Expandable to additional sensor parameters via FSK-modulated digital data stream
  • Dual op-amp 4th order Butterworth filter for FSK generation reduces BOM count
  • Ultra Low power MSP430 consumes less of the 3.5 mA budget allowing more current for sensors in the loop

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Schematic/Block Diagram

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TI Devices (7)

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Part Number Name Product Family Sample & Buy Design Kits & Evaluation Modules
DAC161S997  16-Bit Precision DAC With Internal Reference and 4mA-to-20mA Current Loop Drive  Digital-to-analog converters (DACs)  Sample & Buy View Design Kits & Evaluation Modules
HDC1000  Low Power, 3% Accuracy Digital Humidity Sensor with Integrated Temperature Sensor  Sensors  Not Available View Design Kits & Evaluation Modules
HDC1010  ±2% low-power digital humidity and temperature sensor in WCSP  Sensors  Sample & Buy View Design Kits & Evaluation Modules
LMV342  Dual Rail-To-Rail Output CMOS Operational Amplifier with Shutdown  Operational amplifiers (op amps)  Sample & Buy View Design Kits & Evaluation Modules
MSP430FR5969  16 MHz MCU with 64KB FRAM, 2KB SRAM, AES, 12-bit ADC, comparator, DMA, UART/SPI/I2C, timer  Microcontrollers (MCUs)  Sample & Buy View Design Kits & Evaluation Modules
OPT3001  Digital ambient light sensor (ALS) with high-precision human-eye response  Specialty sensors  Sample & Buy View Design Kits & Evaluation Modules
TPS7A4001  50-mA, 100-V, low-IQ, adjustable low-dropout voltage regulator with enable  Power management  Sample & Buy View Design Kits & Evaluation Modules

CAD/CAE symbols

Part # Package | Pins CAD File (.bxl) STEP Model (.stp)
DAC161S997 Download
HDC1000 Download -
LMV342 Download Download
Download -
Download Download
MSP430FR5969 Download Download
OPT3001 Download Download
TPS7A4001 Download Download

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Technical documentation

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User guide (1)
Title Type Size (KB) Date
PDF 2208 26 Aug 2015
Design files (6)
Title Type Size (KB) Date
PDF 613 24 May 2016
PDF 90 24 May 2016
ZIP 3187 03 Nov 2015
ZIP 655 02 Nov 2015
PDF 1901 02 Nov 2015
PDF 200 02 Nov 2015
Related Tools & Software

Reference Designs (1)

Name Part Number Tool Type
RTD Temperature Transmitter for 2-wire, 4 to 20-mA Current Loop Systems  TIDA-00095  Reference design 

Software development (1)

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