How to Protect Ethernet Networks Against Surge Events

As Ethernet becomes the backbone of industrial communications, the susceptibility of its infrastructure to surge events, such as lightning strikes, poses a critical challenge. Such incidents can induce ground loops and magnetically coupled voltages, potentially crippling operational technology systems.

To maintain Ethernet-connected devices' system integrity and functionality, developers need a robust solution to shield sensitive electronics from destructive energy transfers.

This article briefly describes how surges affect electronic systems. It then introduces protection devices from Analog Devices and shows how to use them to mitigate surge events.

How surge events impact electronic systems

Surge events can occur due to several factors, with lightning being the most dramatic and destructive. Even several miles away, a lightning strike can induce ground loops and magnetically coupled voltages in electronic systems. This transient overvoltage can damage sensitive electronics and disrupt critical operations.

The impact of surge events on electronic systems extends beyond temporary malfunction. These high-energy transfers can cause irreversible damage to circuitry, leading to costly repairs and system downtime. In Ethernet networks, surge events can damage the networking hardware and connected devices, leading to data loss, reduced system performance, and even complete system failure.

The susceptibility of Ethernet infrastructure to surge events stems from its extensive reach and interconnected nature. As Ethernet cables traverse long distances, they pick up electromagnetic disturbances from the environment, including induced voltages and currents from a surge event, reaching devices seemingly isolated from the point of the surge (Figure 1a).

Figure 1: An unprotected Ethernet installation is susceptible to surge events passing through sensitive electronics (a), but using surge-protection design methods such as guard planes can allow a safe path for surge currents (b). (Image source: Analog Devices)

Developers must implement robust surge protection measures to shield sensitive electronics from these high-energy transfers, ensuring system integrity and functionality. This involves protecting critical points in the network with surge protection devices capable of diverting the excess energy away from sensitive components, either by grounding it or dissipating it safely using techniques such as guard planes (Figure 1b).

To help build surge protection into their connected devices, developers rely on advanced design methods such as voltage clamping using a transient voltage suppressor (TVS), isolation approaches, high-frequency filtering, and other techniques. At the same time, successful surge protection requires combining these techniques with specialized components, including Ethernet physical layer (PHY) devices, controllers, and power-sourcing equipment designed to manage the stresses induced by surge events.

A set of solutions from Analog Devices is specifically designed to support surge protection design methods, while meeting the specialized requirements for robust functionality in Ethernet-connected devices.

Building surge protection into Ethernet networks

For organizations transitioning from legacy communications to Ethernet-based connectivity, the emergence of the 10BASE-T1L physical layer Ethernet standard provides the critical link needed to connect edge devices in remote and hazardous locations within the factory using the IEEE 802.3cg standard for 10 megabit per second (Mbps) single-pair Ethernet (SPE) cable. Designed to support these standards, Analog Devices’ ADIN1100 is a low-power, single-port transceiver that supports Ethernet connectivity at distances up to 1,700 meters (m). Consuming only 39 milliwatts (mW), the ADIN1100 combines a comprehensive functional architecture with a hardware interface designed to simplify connecting a host processor to an Ethernet network (Figure 2).

Figure 2: The ADIN1100 provides a complete 10BASE-T1L PHY, simplifying the transition of industrial systems to Ethernet networks. (Image source: Analog Devices)

The ADIN1100’s surge-protection design with integrated power supply monitoring and power-on reset (POR) circuitry contributes to system robustness, ensuring stable operation even in volatile conditions. With Analog Devices’ EVAL-ADIN1100-EBZ evaluation board, developers can quickly assess the ADIN1100’s performance and explore additional surge protection mechanisms.

Along with LED status indicators, buttons, and interface connections, the evaluation board provides test points, a small prototyping area for examining alternative cable connection approaches, and optional isolation transformers or power coupling inductors (Figure 3).

Figure 3: The EVAL-ADIN1100-EBZ ADIN1100 simplifies the evaluation of the ADIN1100’s performance and experimentation with surge-protection design mechanisms. (Image source: Analog Devices)

Industrial Ethernet-powered device controller

Designed for industrial SPE applications, the Analog Devices LTC9111 is an IEEE 802.3cg-compliant, single-pair power over Ethernet (SPoE) powered device controller featuring a wide operating range from 2.3 to 60 volts. The device supports the serial communication classification protocol (SCCP) in systems where the powered device (PD) and power sourcing equipment (PSE) share information about required power classes.

With its support for IEEE 802.3cg, the LTC9111 is built to reduce the effect of surge events, but developers using the device in surge-sensitive applications can include a voltage clamp such as a TVS diode. A TVS combined with the ADIN1100 provides an effective solution for implementing SPoE solutions that can operate across extended distances (Figure 4).

Figure 4: Combined with the ADIN1100, the LTC9111 simplifies SPoE designs, requiring only a few additional components to complete the powered device side of an Industrial Ethernet connection. (Image source: Analog Devices)

SPoE PSE controller

For the power sourcing side of an 802.3cg-compliant application, the LTC4296-1 is a five-port SPoE PSE controller designed for interoperability with 802.3cg PDs in 24 or 54 volt systems. Featuring a 6 to 60 volt input voltage range, the device supports an extensive set of protection capabilities, including the use of external N-channel MOSFETs, foldback analog current limit (ACL), adjustable source and return electronic circuit breakers, and more. For additional surge protection, developers can add a TVS diode, such as the Littelfuse SMAJ58A to mitigate supply spikes (Figure 5).

Figure 5: Complementing the LTC9111 PD controller, the LTC4296-1 five-port SPoE controller simplifies the design of the PSE side of an Industrial Ethernet connection. (Image source: Analog Devices)

Using Analog Devices’ EVAL-SPoE-KIT-AZ evaluation kit, developers can quickly gain PSE controller experience. The kit enables designers to study a complete IEEE 802.3-compliant SPoE application. It comes with LTC4296-1 and LTC9111-based motherboards, each hosting ADIN1100-based plugin shields that connect through an SPE cable (Figure 6).

Figure 6: The EVAL-SPoE-KIT-AZ evaluation kit provides a complete set of hardware boards and cables to evaluate an SPoE application based on the LTC4296-1 PSE and LTC9111 PD controllers and an ADIN1100 10BASE-T1L Ethernet PHY device. (Image source: Analog Devices)

Although the LTC4296-1 PSE controller, LTC9111 PD controller, and ADIN1100 10BASE-T1L Ethernet PHY device enable rapid implementation of IEEE 802.3cg-compliant SPoE solutions, another Analog Devices solution addresses the need for active-clamp controllers.

Active-clamped PWM controller

Designed to enhance the efficiency of supply sources in PoE PD applications, Analog Devices’ MAX5974 series devices are active-clamped, spread-spectrum, current-mode pulse-width modulation (PWM) controllers. The MAX5974 series devices are offered in multiple variations. For example, the MAX5974D is designed to support output regulation using traditional optocoupler feedback. In contrast, the MAX5974B is designed to support output regulation without an optocoupler, while enabling the coupled inductor output to derive converter supply input (IN) (Figure 7).

Figure 7: Analog Devices’ MAX5974B simplifies active-clamped converter design by eliminating optocouplers in the feedback, and deriving converter input (IN) voltage from the coupled inductor output. (Image source: Analog Devices)

The feed-forward, maximum duty-cycle clamp integrated into MAX5974 devices ensures that the maximum clamp voltage remains independent of the line voltage during transient conditions. The device’s cycle-by-cycle current limit capability helps further protect sensitive electronics. When the device detects that the peak current limit has been reached and sustained past a threshold duration, it turns off its main switch gate-drive output (NDRV) and active clamp switch gate-drive output (AUXDRV) temporarily, allowing overload current to dissipate before attempting a soft start.

Applying a broad approach to surge protection

These products enable a broad approach to surge protection in Ethernet networks. The ADIN1100 ensures long-reach and low-power operation, serving as a robust foundation for the network. The LTC9111 and LTC4296 controllers work in tandem to manage power delivery and protect against surges at both the PD and PSE levels. The MAX5974 complements this setup by ensuring efficient power conversion and reducing the potential for energy waste during surge events.

By implementing these products in coordination, developers can significantly enhance the surge protection capabilities of Ethernet networks. This integrated approach safeguards the hardware and ensures uninterrupted communication and operational continuity.

Conclusion

Ethernet offers significant advantages for industrial communications, but lengthy cable runs leave sensitive electronics vulnerable to surge events. Using a set of devices and development resources from Analog Devices, developers can rapidly implement Ethernet connectivity capable of resisting the effects of surge events.