A、Overview of IO-LINK Technology

IO-LINK is the world's first IEC 61131-9 standardized digital interface for sensor and actuator communication, and it is a key supporting technology for the transformation of intelligent factories. It enables point-to-point bidirectional communication between sensors and controllers through conventional three-wire cables, without the need for complex addressing or special cables. It combines the functionality of analog signals with the intelligence of Ethernet communication, and has the same cost as traditional sensors. It has been widely applied in industrial automation scenarios such as automotive manufacturing, photovoltaic lithium batteries, food and beverage, and industrial robots. This technology can break the "data island" of traditional sensors, bidirectionally transmitting detection data, equipment status, and diagnostic information, providing core support for factory predictive maintenance, fault diagnosis, and energy management. It is also a key connection link between field transmitters, sensors, PLCs, and DCS control systems.

B、Three Challenges in the Design of IO-LINK Sensors

In the current design process of IO-LINK sensors, heat dissipation, size, and EMC testing are the three core bottlenecks that limit their reliability and applicability. These three aspects are interrelated and mutually influential, and need to be jointly addressed through systematic protective design.

1、Heat Dissipation: The problem of power dissipation in small packages

IO-LINK sensors are mostly used at the edge of industrial equipment; for apply into the limited installation space, they generally use micro-packaging designs. However, the reduction in package size directly leads to a limited space for power dissipation, which easily causes the equipment to overheat, thereby affecting the communication stability and the lifespan of components.

2、Size: The demand for miniaturization integration in edge environments

Under the backdrop of Industry 4.0, IO-LINK sensors are evolving towards miniaturization and integration. The limited installation space of precision machine tools and industrial robots imposes strict requirements on the overall size of the sensors (including the core transceiver and protective components). There is a dilemma in miniaturization: reducing the packaging of the transceiver will weaken its inherent ESD and surge protection capabilities. Extra protective components need to be added. Small-sized, highly integrated protective components need to be selected to be compatible with mainstream small-package IO-LINK transceivers. While not increasing the size, the protection shortcomings need to be remedied.

3、EMC Testing: Reliability Protection in Harsh Industrial Environments

The harsh factors such as electromagnetic interference, ESD, surges, and EFT in industrial environments can easily impact the communication and power interfaces of IO-LINK sensors, leading to data errors, equipment failures, and even damage. EMC testing is an essential part of the design and the core of protection for these sensors. Among them, ESD originates from human operations, equipment start-stop, etc., with voltages reaching tens of thousands of volts. A brief impact can cause the transistors in the receiver and transmitter to be broken, disrupt the logic of the communication chips, and result in data packet loss, increased bit error rate, and even sensor failure. The protection of the receiver and transmitter alone is insufficient to withstand it; it needs to be combined with external protective components to build a multi-layer protection system.

C、IO-LINK Sensor Leiditech Comprehensive Protection Solution

Based on the three major design challenges, Leiditech EMC team combined the IEC 61000 standard with the accumulated industrial protection technologies to create a comprehensive protection solution of "selection adaptation + multi-layer protection + miniaturization integration + heat dissipation optimization", precisely solving the problems of heat dissipation, size, and EMC, ensuring that the IO-LINK sensors can operate stably in harsh industrial environments, while meeting the requirements of miniaturization and low-cost design.

1)    Heat dissipation optimization solution: Low power consumption selection combined with PCB optimization coordination

a)    Key component selection: It is recommended to choose low-power IO-LINK transceivers, combined with Leiditech low-leakage current TVS diodes, to reduce the additional power consumption of protective components and alleviate the heat dissipation pressure.

b)    PCB heat dissipation design: Optimize the PCB layout, reserve heat dissipation pads for core components, and increase the heat dissipation area; select high-heat dissipation performance materials to reduce thermal resistance; in high-power scenarios, additional heat dissipation copper foil or integrated micro heat sinks can be added to improve heat dissipation efficiency.

2)    Dimension optimization solution: Miniaturization integration + Compatible adaptation design

a)    Miniaturization selection of protective components: The sensor slave station is limited by miniaturized packaging. The 0201/0402 ultra-small ESD/TVS devices are preferred. For the three-wire communication interface (L+, C/Q, L-), a minimalist protection design is adopted, balancing protection performance and low power consumption and heat dissipation requirements.

b)    High integration protection design: The lightning barrier integrated protection components can be used. A single component integrates multiple protection functions, replacing the traditional combination of multiple components, saving PCB space and simplifying the circuit.

c)     Standardized compatibility design: The solution follows the IO-LINK transceiver pin and interface specifications. The protective components do not affect the operation and communication performance of the transceiver, and are compatible with the IO-LINK master stations of various manufacturers, ensuring the universality and interchangeability of the sensor, and reducing design and production costs.

3)    Protection Plan: Multi-level Protection + Comprehensive Scenario Coverage

Establish a multi-level safety protection system consisting of "front-end buffering, core protection, and back-end clamping". For industrial hazards such as ESD, surges, and EFT, use Leiditech electronic protection components to ensure that the sensors comply with the IEC 61000 series standards and are suitable for various harsh industrial environments.

l  Power supply ports of the IO-LINK master station at all levels:

Shanghai Leiditech Electronic has designed a "overvoltage + overcurrent + anti-backflow" triple protection system for 24V industrial power supplies, which can protect against static electricity, surges and EFT. IO-Link communication takes place between a host and a device (sensor or actuator). Communication requires the use of a three-wire interface (L+, C/Q and L-). In the IO-Link system, the power supply range of the host is from 20V to 30V, and the power supply range of the device (sensor or actuator) is from 18V to 30V.

·         Overvoltage protection: The positive and negative poles of the power input are connected in parallel with the Leiditech SMBJ33CA TVS diode. The clamping voltage is ≤ 54V (which should be lower than the maximum withstand voltage of the protected DC-DC component in the 24V power system. For example, if using 36V or 40V DC-DC, the Leiditech burst-type TVS series can be selected. The low clamping voltage effectively protects the downstream). The current capacity is 11.3A (10/1000μs), and it can quickly discharge transient overvoltages.

·         Overcurrent protection: Series Leiditech PPTC. It automatically disconnects when there is an overcurrent (such as a short circuit), and resumes operation after the fault is resolved, preventing the power module from being damaged.

·         Anti-reverse connection: Implement polarity reverse connection protection by using PMOS (suitable for high-power scenarios above 20A, recommended LM5D28P10 type PMOS from Leiditech Electronic) or low-dropout Schottky diode (suitable for low-power scenarios, such as SK56C from Leiditech Electronic, 60V/5A).

Leiditech apply SMDA33CDN and SD03CW to meet the electrostatic protection requirements for the VCC power supply of 3.3V. SD0581D3W/SD05C meets the electrostatic protection requirements for the DC 5V power supply, and SD12C/SMAJ15CA meets the electrostatic surge protection requirements for the DC 12V power supply. It complies with IEC61000-4-2, level 4, and can withstand contact discharge of 30KV and air discharge of 30KV.

Digital communication interface:

l  I2C interface:

￮  Working voltage: Consistent with the supply voltage. Different voltage levels require level conversion.

￮  Protection concerns: ESD (electrostatic discharge) for SDA/SCL pins (human static electricity, machine static electricity), surge caused by bus conflicts;

￮  Shanghai Leiditech Electronic recommends SMC12 integrated ESD diodes, with small package, low capacitance, large current protection, meeting IEC61000-4-2, level 4, capable of withstanding contact discharge of 30kV and air discharge of 30kV.

l  SPI interface:

￮  Protection concerns: ESD on all communication pins, surge interference on clock signals causing data misalignment

￮ Recommended by Leiditech: SMC12 integrated ESD diodes, meeting requirements of small package, low capacitance, high current protection, meeting IEC61000-4-2, level 4, capable of withstanding 30kV contact discharge and 30kV air discharge.

l  UART interface:

￮  Working parameters: Baud rate (9600/19200/115200 are commonly used), Asynchronous transmission

￮  Protection concerns: ESD on TX/RX pins. Leiditech recommended to use ESDA33CP30, etc. The package is DFN1006, used to provide 3.3V static discharge surge protection for the MCU serial port UART in a compact PCB circuit, meeting IEC61000-4-2 level 4, capable of withstanding 30KV contact discharge and 30KV air discharge.

Shanghai Leiditech Electronic, as a professional supplier of protective components, can provide all the compatible components of this solution (TVS diodes, ESD diodes, GDT, MOV, etc.). Relying on its professional technical team, it offers one-stop technical support such as customized protection design and component selection guidance for customers, helping projects to be implemented quickly and promoting the upgrading of industrial automation towards intelligence, miniaturization and reliability.