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Programmable logic controllers (PLC)

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Programmable logic controllers (PLC)

Programmable Logic Controllers (PLCs) are the key application enabling factories to operate in an automated way. PLC is typically built up as a modular system consisting of several blocks, such as control unit (often called central processing unit, CPU) and multiple Input / Output or other function modules (expansion modules). Control unit communicates with the expansion modules over a dedicated and usually a customer-specific bus called backplane interface. Control unit operates in cycles and periodically exchanges data with the expansion modules. The data are processed in the control unit in-between each consecutive cycles. The input / output modules make an interface / connection to the factory process side and provide information about various physical variables detected by sensors on one side and enable to interact with the automation process through different actuators driving on the other side. Each needs to be integrated in the complete automation system and therefore provides connectivity functions to various fieldbuses or industrial ethernet.

Processing performance, speed and integration

Processing performance, speed and integration

With increasing complexity and continuous evolution of automated production lines, also the automation system requirements are rising rapidly. More data need to be exchanged over the input / output and other function interfaces and CPU cycles are expected to be shorter. Moreover, the systems are supposed to be well synchronized and to operate in a deterministic way.

The data exchange as well as communication is done in real-time with reduced latencies and minimized jitter. This strengthens the requirements on processing performances as well as connectivity architectures and the way of implementation. The industrial factories are often a very harsh environments in terms of pollution such as dust, humidity, chemical but also electro-magnetic field, noise and other disturbances.

Applications must be extremely immune vs. such tough conditions and disturbances and provide reliable operation over their very long lifetimes. Long-term availability, safety and security are another challenge for PLC designs.

Our products and solutions

ST has an extensive offer of STM32, 32-bit microcontrollers and microprocessors and the essential accompanying devices like EEPROM, RTCs and Supervisors and dedicated products ensuring the systems security when connected to a cloud.

Input / output modules can benefit from our highly robust current limited terminations (CLT) significantly reducing power dissipation and intelligent power switches (IPS), enabling reliable driving of industrial loads, able to comply with safety regulations (SIL) and offering also embedded galvanic isolation for high immunity and the most compact designs. Signal conditioning in analog peripherals can be solved by new operation amplifiers, current sensing chips or comparators.

Different application blocks supply circuits can be developed using ST power management ICs. High level of protection tailored according to the exact requirements can be granted thanks to the Transient Voltage Suppressors (TVS) or other protection devices. An essential part of the system are communication interfaces, which enable integration to factory automation system. ST provides solutions for both – wired connectivity through various fieldbuses and wireless connectivity technologies.