96-Channel Bidirectional Digital Input Module Reference Design for PLC


Design files


This reference design is a compact implementation of 96 isolated digital input channels using the ISO1212, an isolated digital input receiver. This design shows the current limit feature of the ISO1212 device which has better thermal performance than traditional optocoupler solutions. This design makes a digital input board with multiple channels more compact and decreases board temperature (less than 50°C). A MUX and decoder with the ISO1212 device decreases the number of pins of the microcontroller from 96 to 8. The design was tested with 100-kHz input signals (200- kbit) per channel. The design uses less than 7.3 W of input power which results in less heat dissipation. All signals are designed to withstand ESD, EFT, and surge events according to IEC6100-4.

  • 96-channel bidirectional digital input module
  • Voltage Inputs: 24-VDC Range, Limited to 3.1 mA Per Channel
  • Compact and Low Temperature Rise (< 50°C at 1hour) Design with all 96 channels on
  • Serial Output Option
  • Tested to 0.5 kV, 42 Ω IEC 61000-4-5 surge test for industrial signal lines

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.

TIDUEA4.PDF (4699 K)

Reference design overview and verified performance test data

TIDRWP3.PDF (1845 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

TIDRWP7.ZIP (2899 K)

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

TIDCES3.ZIP (1005 K)

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

TIDRWP6.PDF (6334 K)

PCB layer plot file used for generating PCB design layout


Includes TI products in the design and potential alternatives.

Analog switches & muxes

CD74HC40675-V, 16:1, 1-channel analog multiplexer

Data sheet document-pdfAcrobat PDF
Digital demultiplexers & decoders

CD74HC238High Speed CMOS Logic 3-to-8 Line Decoder Demultiplexer Inverting and Non-Inverting

Data sheet document-pdfAcrobat PDF open-in-new HTML
Isolated digital inputs

ISO1212Dual-channel Isolated 24-V to 60-V digital input receiver for digital input modules

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

Technical documentation

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* Design guide 96-Channel Bidirectional Digital Input Module Reference Design for PLC Jul. 11, 2018

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