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Single- and dual-line self-powered digital input current limiter in SOT23-8L and QFN-16L packages

The self-powered CLT03-1SC3 and CLT03-2Q3 digital input current limiters drastically reduce power dissipation while improving EMC robustness in industrial automation and process control.

In high-density, compact, multi-channel modules, power consumption and associated heat dissipation is a critical consideration. An efficient current limitation should be applied in compliance with IEC 61131-2 specifications.

The CLT03-1SC3 and CLT03-2Q3 are industrial digital input current limiters that convert a 24 V digital input to 3 mA current to drive optical isolators or non-isolated LVTTL interfaces.

With a wide input voltage range up to 60 V, a built-in test pulse generator, and extra smart power limitation during overvoltage, the CLT03-1SC3 and CLT03-2Q3 simplify SIL certification for safety applications.

Key features

vibration sensor with 10 year longevity
  • Accurate current limitation for Type 1 and Type 3 IEC 61131-2 digital inputs
  • Self-powered, eliminating the need for an external field-side power supply
  • 60 V maximum input voltage
  • Able to interface high side or low side sensors (sinking or sourcing inputs)
  • Over-voltage protected with extra power dissipation reduction above nominal operating conditions


  • Flexibility: No need for an external field-side power supply!
  • Single- and dual-channel versions
  • Compatible with high/low-side sensors, opto-couplers and CMOS output
  • Safety: 60V tolerant, embedded configurable test pulses, channel isolation, indicator LED on process side
  • Space saving compared to discrete implementation
  • Reduced BOM costs

Application examples

industrial automation Process control & Industrial automation
programmable logic controller Programmable Logic Controllers (PLC)
motor control Motor control
  • CNC controls
  • Remote input modules
  • Current sourcing inputs
  • ...

How to test & prototype with CLT03 Series

Choose a development kit to start testing the capabilities and features of CLT03-1SC3 and CLT03-2Q3:

Isolated and non-isolated digital inputs on evaluation board

Featuring reduced power dissipation and improved EMI robustness for safer and more reliable operation, the board helps designers evaluate circuit protection strategies for factory automation and build solutions with greater I/O module density.

Explore ST's complete TVS product portfolio and easily find the device that best fits your application using the parametric or series search engine. Available for Android™ and iOS™.

protect finder


Self-Powered Digital Input with CLT03-2Q3

This presentation looks at what functions and characteristics you should consider in digital input current limited termination devices depending on your application. It also talks about the differences between integrated and discrete solutions and provides an overview of our portfolio.

The CLT03 series of current limiters drastically reduces input losses while improving EMC robustness.

PDF current limiters self powered
st blog

Too often, companies forget that industrial applications are also getting smaller and denser. While many understand why consumer products pack more features, industrial control systems aren’t exempt from such trends. Hence, ST launched the CLT03-1SC3 and CLT03-2Q3, two current limiters for digital inputs that vastly reduce heat dissipations.

Learn how engineers working on a wide range of process, industrial, and building automation applications can better protect their equipment and ensure the safety of their personnel through the use of a robust, low-power approach based on self-powered digital input current limiters.

PDF whitepaper smart digital input factory automation process
Industrial PLC evaluation board HMI

Targeting compact PLC applications in factory automation, this board features a powerful HMI thanks to its 3.5” TFT touchscreen.

It is built around a high-performance 144-pin STM32F7 MCU that handles the industrial IOs on one side and the TouchGFX display technology on the other side, implementing the ladder logic programming code and several additional options.