TIDA-00247

Single Chip 2-Wire Loop Powered, 4 to 20mA Current Loop RTD Temperature Transmitter Reference Design

TIDA-00247

Design files

Overview

In general, for portable 2-wire 4 to 20mA current loop applications, the system power consumption needs to be considered carefully. The conventional approach of using a high bridge excitation voltage and an operational amplifier to achieve a full-scale ADC input voltage increases chip count and overall power consumption. An additional external voltage regulator is also needed to excite the bridge sensor and supply the microcontroller from the same voltage source. Since the goal for this reference design is to maintain low power consumption and low cost solution. This solution utilizes the integrated ADC and operational amplifiers (OAs) of a microcontroller. In order to cut down the cost, the ADC/DAC use the main supply voltage as its reference voltage instead of including an external reference or selecting a more expensive ADC/DAC that features an internal reference. Leveraging the integrated peripherals of MCU enables low component count and low cost. This reference design is based on a mixed signal microcontroller, specifically an MSP430F2274.

Features
  • Analog functionality fully integrated into microcontroller
  • Sensor input compatible with 2-wire PT100 RTD probe only
  • Temperature range for RTD -200°C to +850°C
  • Input power supply range: 10V to 33V DC
  • 4 to 20mA current loop output signal
  • Maximum measured error: better than ±2.5ºC
  • Implements ratiometric measurement
  • Design to meet IEC 61000-4 requirement
  • Operating temperature range -40°C to +85°C

A fully assembled board has been developed for testing and performance validation only, and is not available for sale.

Design files & products

Design files

Download ready-to-use system files to speed your design process.

TIDU751A.PDF (10401 K)

Reference design overview and verified performance test data

TIDRCR5.PDF (653 K)

Detailed schematic diagram for design layout and components

TIDRCR6.PDF (43 K)

Complete listing of design components, reference designators, and manufacturers/part numbers

TIDRCR8.ZIP (1222 K)

Files used for 3D models or 2D drawings of IC components

TIDC894.ZIP (301 K)

Design file that contains information on physical board layer of design PCB

TIDRCR7.PDF (161 K)

PCB layer plot file used for generating PCB design layout

Products

Includes TI products in the design and potential alternatives.

Linear & low-dropout (LDO) regulators

TPS7A16100-mA, 60-V, ultra-low-IQ, low-dropout (LDO) voltage regulator with power good and enable

Data sheet document-pdfAcrobat PDF open-in-new HTML
MSP430 microcontrollers

MSP430F227416 MHz MCU with 32KB Flash, 1KB SRAM, 10-bit ADC, 2 OpAmp, I2C/SPI/UART

Data sheet document-pdfAcrobat PDF

Technical documentation

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Type Title Date
* Design guide Temperature Transmitter on Single Chip Mixed-Signal MCU (Rev. A) Jan. 30, 2015
Technical article Leveraging MSP430™ FRAM MCUs with integrated configurable analog in modern-day factories Aug. 30, 2019
Technical article A single-chip 4-20mA temperature transmitter at embedded world 2015 Feb. 25, 2015

Related design resources

Reference designs

REFERENCE DESIGN
TIDA-00095 RTD Temperature Transmitter for 2-wire, 4 to 20-mA Current Loop Systems TIDA-00165 Small Form Factor, 2-Wire 4 to 20mA Current Loop RTD Temperature Transmitter Reference Design TIDA-00168 Thermocouple AFE Using RTD or Integrated Temperature Sensor for Cold Junction Compensation (CJC) TIDA-00189 Isolated Loop Powered Thermocouple Transmitter Reference Design TIDA-00459 Highly Efficient Power & Data Transmission for Isolated Low Power Applications Reference Design

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