Reference Design for Protection of PLC Based Circuits.


  • The design help devices from quick surge current product in PLC inputs and other industrial instruments.
  • The design features a compact design and sturdy protection.

Texas Instruments released a reference design for a protection module for PLC devices. This design is based on TIDA-01438 Surge Protection device which is available in the Texas Instruments page. The reference design is focused on providing a protection circuit for industrial instruments and control devices where the surge voltages go up-to 1 kilo-volt.

The reference design is based on using the 33-V series protection circuits which claim to have higher accuracy and low leakage current for the target devices. Surge current is sudden rise and fall in current over a short duration of time above normal or rated value. This phenomenon can be observed in the AC or DC circuit.

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Surge current is generally generated by internal and external conditions. Internal conditions such as the impulse currents which are generated by the internal capacitor in the electric device. The external conditions referred to as surge current is generated from the lightning. As it exceeds the current handling capacities of a device, circuit protection should be used to save the device from damage.

There are some key parameters for designing a protection circuit such as Operating Voltage, Channel capacity, Operating temperature, Input impedance etc which are important factors for the design.

The features provided by this reference design for a stable protection circuit are –

  • The designed circuit has a dimension of 159 mm × 55 mm which is a suitable dimension for industrial automation and control devices.
  • The design offers an operating voltage of 16 Volts to 33 Volts. This wide range increases the implementation of the circuit in DC-driven applications.
  • The design provides two different channels for use with a power consumption capacity of 400 milli-Watt per channel.
  • The operating Voltage for the circuit ranges from -40 degree Celcius to +85 degree Celcius for the ideal as well as working modes.
  • The input impedance of the circuit is 86.1 Kilo-Ohms. Input Impedance is the ratio of voltage across the input terminals to the current flowing through the input terminals.
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All these features are helpful while designing an efficient protection system for PLC-based and measurement-based devices. The area of implementation for the design is large but currently tested for use with Analog PLC input devices.

All the documentation including Schematics, design guide and Design files can be downloaded here.



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