4-20mA Analog Input Module Reference Design for Safety Applications


Design files


TIDA-00548 is an isolated dual-channel 4- to 20-mA analog input reference design, which can be used as a sub-part for functional safety programmable logic controllers (PLCs). This reference design delivers digitized input values using a 32-bit high-performance analog-to-digital converter (ADC). The RM4x dual-core ARM® Cortex®-R4 based CPU with lockstep technology and built-in self-tests (BIST) compares the converted values of up to nine selectable analog input signal chain paths. The dual-input approach with two separate burden resistors allows redundant measurement of either a single 4- to 20-mA loop or two independent loops. Hercules™ RM ARM Cortex-R based MCUs for functional safety applications help to develop systems according to IEC 61508 SIL 3.

  • Two channel 4- to 20-mA current measurement for redundancy with full-scale error less than ±0.01%
  • Two ADC references (external and internal)
  • Utilizes ADC built-in features such as test DAC, secondary ADC, analog signal level alarm, SPI CRC, timeout and more
  • Hercules RM ARM Cortex-R based MCU (for development of IEV 61508 functional safety applications)
  • Isolator shutdown upon failure provides reliable notification to backend
  • All integrated circuits: MTBF greater 4·10^8
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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.

TIDUC03.PDF (1011 K)

Reference design overview and verified performance test data

TIDROH9.PDF (1641 K)

Detailed schematic diagram for design layout and components


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


Detailed overview of design layout for component placement

TIDROI3.ZIP (2468 K)

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


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

TIDROI2.PDF (3870 K)

PCB layer plot file used for generating PCB design layout


Includes TI products in the design and potential alternatives.

AC/DC & DC/DC converters (integrated FET)

TPS621703–17V 0.5A Step-Down Converter with DCS-Control in 2x2 QFN package

Data sheet: PDF | HTML
Arm Cortex-R MCUs

RM41L23216/32 Bit RISC Flash MCU, Arm Cortex-R4F

Data sheet: PDF | HTML
Digital isolators

ISO7141CCQuad-channel, 3/1, 50-Mbps digital isolator

Data sheet: PDF | HTML
Instrumentation amplifiers

INA826Precision, 200-μA Supply Current, 36-V Supply Instrumentation Amplifier

Data sheet: PDF | HTML
Load switches

TPS27082L8-V, 3-A, 44-mΩ load switch with adj. rise time and hysteresis

Data sheet: PDF | HTML

CSD18534Q5A60-V, N channel NexFET™ power MOSFET, single SON 5 mm x 6 mm, 9.8 mOhm

Data sheet: PDF | HTML
OR gates

SN74LVC1G3321-ch, 3-input 1.65-V to 5.5-V 32-mA drive strength OR gate

Data sheet: PDF
Precision ADCs

ADS126332-bit 38-kSPS 10-ch delta-sigma ADC with PGA, VREF and auxiliary ADC for factory automation

Data sheet: PDF | HTML
Precision op amps (Vos<1mV)

TLV333Single, 350-kHz, low-noise, RRIO, CMOS operational amplifier for cost-sensitive systems

Data sheet: PDF | HTML
Series voltage references

REF50303-V, 3-µVpp/V noise, 3-ppm/°C drift precision series voltage reference

Data sheet: PDF | HTML
Transformer drivers

SN6501Low-noise, 350-mA, 410-kHz transformer driver for isolated power supplies

Data sheet: PDF | HTML
XOR (exclusive OR) gates

SN74LVC2G862-ch, 2-input, 1.65-V to 5.5-V XOR (exclusive OR) gates

Data sheet: PDF

Start development

Design tools & simulation

Simulation model

TIDA-00548 Simulation (ILim) — TIDM048.ZIP (33 K)

Technical documentation

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Type Title Date
* Design guide 4- to 20-mA Analog Input Module for Safety Applications Design Guide Oct. 24, 2016

Related design resources

Design tools & simulation

TINA-TI SPICE-based analog simulation program

Support & training

TI E2E™ forums with technical support from TI engineers

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