Reliable Ethernet Physical Layer Solution for Time-Limited Communication in Harsh Industrial Environments

Why should industrial applications adoptEthernet?

More and more industrial systems are adopting Ethernet connectivity to address key Industry 4.0 and smart factory communication challenges facing manufacturers, including data integration, synchronization, terminal connectivity and system interoperability challenges. The Ethernet-connected factory increases productivity by enabling connectivity between information technology (IT) and operational technology (OT) networks, while increasing production flexibility and scalability. In this way, all areas of the plant can be monitored using a seamless, secure, high-bandwidth network that supports time-limited communications.

Scale computing and reliable communication infrastructure are the lifeblood of the connected factory. Today’s networks are challenged with growing traffic loads and interoperability between numerous protocols that require complex and power-hungry gateways to transform traffic throughout the plant. Industrial Ethernet addresses these interoperability issues within the same network by seamlessly delivering critical deterministic performance to the end-point at the factory edge. There has been a lack of suitable Ethernet physical layers (PHYs) designed for reliable industrial environments in the past. Designers of industrial communication equipment have long had to use consumer-grade standard Ethernet PHYs developed for the mass market. In the era of Industry 4.0, where the number of end nodes is accelerating, and determinism is extremely important for enabling connected factories, enhanced industrial-grade Industrial Ethernet PHYs are critical.

IT and OT Ethernet Connectivity

Since Ethernet is a widely supported, scalable, and flexible high-bandwidth communications solution, it has long been the communications choice for IT. In addition, it has the interoperability benefits brought by the IEEE standard. A key challenge, however, in enabling seamless connectivity between IT and OT networks and based on Ethernet technology is how to deploy in harsh industrial environments that require time-critical connectivity.

Industrial Ethernet Applications and Ethernet Deployment Challenges

Figure 1 shows a connected mobile application based on an industrial Ethernet connection in a smart factory. Multi-axis synchronization and precise motion control are essential for high-quality production and machining in smart factories. With the increasing demands on production capacity and output quality, servo motor drives also require faster response times and higher drive precision. Increased system performance requires tighter synchronization of servo motor shafts used in end equipment. Real-time 100 Mb Ethernet is widely used in today’s motion control systems. However, synchronization only involves data communication between network masters and slaves.

The network needs to support synchronization across network boundaries to the application, from sub-1 μs times to PWM outputs within servo motor control. This improves machining and production accuracy for multi-axis applications such as robotics and CNC machine tools with higher data rates Gigabit Industrial Ethernet and IEEE 802.1 Time Sensitive Networking (TSN). Using the real-time Industrial Ethernet protocol, all devices can be connected to a high-bandwidth aggregated network for edge-to-cloud connectivity.

Reliable Ethernet Physical Layer Solution for Time-Limited Communication in Harsh Industrial Environments

Figure 1. Connected mobile applications via Industrial Ethernet.

In industrial environments, the main challenges for network installers deploying Ethernet are robustness and high ambient temperatures. High voltage transients from motors and production equipment around long cable runs can damage data and equipment. Successful deployment of Industrial Ethernet (shown in Figure 1) requires an enhanced Ethernet PHY technology that requires robust performance, low power consumption, low latency, a small package, and the ability to operate in noisy, high-temperature environments. This article will discuss the challenges of deploying Ethernet PHY solutions in the connected factory.

What is the Industrial Ethernet Physical Layer?

The Industrial Ethernet PHY is a physical layer transceiver device that transmits and receives Ethernet frames according to the OSI network model. In OSI mode, Ethernet covers part of layer 1 (physical layer) and layer 2 (data link layer) and is defined by the IEEE 802.3 standard. The physical layer specifies electrical signal types, signal speeds, media, and network topology. It implements the Ethernet physical layer portion of the 1000BASE-T (1000 Mbps), 100BASE-TX (100 Mbps, copper), and 10BASE-T (10 Mb) standards.

The data link layer specifies how to communicate over the medium, as well as the frame structure for transmitting and receiving messages. It just means how the bits are separated off the wire and into the bit arrangement in order to extract the data from the bit stream. For Ethernet, this is called Media Access Control (MAC) and will be integrated into the host processor or Ethernet switch. For example, the fido5100 and fido5200, two ADI embedded, dual-port Industrial Ethernet embedded switches, are used for Layer 2 connectivity that supports multiprotocol, real-time Industrial Ethernet device connectivity.

Ethernet Physical Layer Requirements for Industrial Applications

1: Power consumption and higher ambient temperature

Ethernet interconnect devices in industrial applications are often packaged in IP66/IP67 sealed enclosures. IP rating refers to the resistance of electrical equipment to water, dirt, dust and sand. The first number after IP is the level of resistance to solids assigned by the IEC. Here, 6 means that no harmful dust or dirt has penetrated into the device after 8 hours of direct contact with the substance. Water-resistance ratings 6 and 7 follow. 6 means protection against water seepage in a powerful jet stream, while 7 means the device can be submerged in 1 meter of fresh water for 30 minutes.

With these sealed enclosures, the two main challenges for Ethernet PHY devices are power consumption and higher ambient temperatures due to the reduced thermal conductivity of the enclosure. Deploying Industrial Ethernet requires the use of Ethernet PHY devices that operate up to 105°C with very low power consumption.

Typical Industrial Ethernet networks are deployed in linear and ring topologies. Compared to star networks, these network topologies reduce wiring length and leave redundant paths in ring networks. Each device connected to a linear or ring network requires two Ethernet ports to pass Ethernet frames along the network. In these use cases, Ethernet PHY power consumption becomes more important because each interconnected device has two PHYs. Gigabit PHY power consumption has a significant impact on total power consumption, while low-power PHYs can provide more of the available power budget for the FPGA/processor and Ethernet switch in the device.

Figure 2. Low-power industrial Ethernet PHY device.

Figure 3. Ethernet PHY latency in an industrial Ethernet network.

Looking at the example in Figure 2, the device has a power budget of 2.5 W, including an FPGA, DDR memory, and an Ethernet switch that requires a power budget of 1.8 W. This leaves only 700 mW of available power budget for both PHYs. To meet the thermal requirements of the device, a Gb PHY with a power consumption of

2: EMC/ESD robustness

In harsh factory conditions where production equipment noise can generate high voltage transients and equipment installers and operators can introduce electrostatic discharge events, industrial network cabling paths can be up to 100 meters long. Therefore, robust and reliable physical layer technology is critical to the successful deployment of Industrial Ethernet.

Industrial equipment typically needs to meet the following EMC/ESD IEC and EN standards:

u IEC 61000-4-5 surge

u IEC 61000-4-4 Electrical Fast Transient Burst (EFT)

u IEC 61000-4-2 ESD

u IEC 61000-4-6 Conducted immunity induced by radio frequency fields

u EN 55032 Electromagnetic Radiation Disturbance

u EN 55032 Conducted Disturbance

The costs associated with certifying products to these standards are high, and if design iterations are required to meet any of these standards, new product introductions are often delayed. Using PHY devices that have been tested to IEC and EN standards can significantly reduce new product development costs and risks.

3: Ethernet PHY Latency

For applications requiring real-time communication (shown in Figure 1), where precise motion control is important, PHY latency can also be an important design specification, as it is a critical part of the overall industrial Ethernet network cycle time. The network cycle time is the communication time required by the controller to collect and update data from all devices. Reducing network cycle time enables higher application performance in time-limited communications. A low-latency Ethernet PHY helps minimize network cycle time, allowing more devices to connect to the network.

Since linear and ring networks require two Ethernet ports to transfer data from one device to the next, the effect of Ethernet PHY latency is also doubled for devices with two ports (data-in port/data-out port) , see Figure 3. In a network with 32 devices (64 PHYs), if the PHY latency is reduced by 25%, this reduction in Industrial Ethernet PHY latency will have a significant impact on the number of connectable nodes and the Industrial Ethernet network performance (cycle time) Impact.

4: Ethernet PHY data rate scalability

It is also important to use Industrial Ethernet PHY devices that support different data rates: 10 Mb, 100 Mb and 1 Gb. The connection between the PLC and the motion controller requires a high-bandwidth Gigabit (1000BASE-T) TSN Ethernet connection. Field-level connectivity employs an Ethernet connection running the Industrial Ethernet protocol in a 100 Mb (100BASE-TX) PHY. For end node/edge node connections, there is a new physical layer standard in IEEE 802.3cg/10BASE-T1L that supports a low-power Ethernet PHY at 10 Mb bandwidth over a single twisted pair cable up to 1 km technology and can be used in intrinsically safe applications in process control. See Figure 4 for the need for process control Ethernet connectivity and scalable Ethernet PHY data rates from PLC to end node actuators and field instrumentation.

Figure 4. Process control, seamless cloud connection technology.

5: Solution size

As Ethernet technology proliferates to the edge of industrial networks, interconnected nodes are becoming smaller in size. The product size of Ethernet interconnected sensors/actuators can be very small, thus requiring the PHY to be placed in a small package developed for industrial applications. The LFCSP/QFN package with 0.5mm pitch has proven to be more reliable, eliminating the need for an expensive PCB manufacturing process, and the exposed bottom pad can be used in higher ambient temperature conditions, increasing power dissipation.

6: Product durability

Product longevity is a concern for industrial equipment manufacturers, as their equipment typically lasts more than 15 years in the field. So product discontinuation means redesigning a new product, which is costly and time-consuming. Industrial Ethernet PHY devices must have long product lifetimes, which are often not supported by consumer, mass market, Ethernet PHY vendors.

Overview of Industrial Ethernet PHY Requirements for Reliable Industrial Ethernet Applications

Table 1. Consumer and Industrial Ethernet PHY Requirements

ADIN1300: EMC/ESD functional performance classification:

Class A

■ Links are not broken.

■ No more than two consecutive lost or erroneous packets. *

■ The system must be functional and error-free after stress testing without user intervention.

Class B

■ Links are not broken.

■ Tolerate packet loss and erroneous packets.

■ The system must be functional and error-free after stress testing without user intervention.

Class C

■ The link is broken during tests and/or when the system requires user intervention. For example, reset or reboot to resume normal operation after a stress test.

*Please note that functional testing software cannot determine if problem packets are contiguous.

New Industrial Ethernet PHY Technology

Analog Devices recently announced two new industrial Ethernet PHYs that operate reliably in harsh industrial conditions with ambient temperatures up to 105°C. The company has been committed to industrial end market applications, ensuring the development of new products with long production life for industrial applications. The ADIN1300 and ADIN1200, developed specifically to address the challenges described in this paper, have the following enhanced PHY features:

·Enhanced link down detection to detect link down within 10 µs

■ Real-time Industrial Ethernet protocol requirements (eg EtherCAT®)

·Packet start detection supports IEEE 1588 timestamps

■ Accurate timing is required throughout the network

·MDI pin provides enhanced ESD protection

■ RJ-45 connector is ESD robust

·PHY startup time:

■ Time from power good to management interface/register available

·On-chip power monitor

■ Improved system stability at power up

See Table 2 for an overview of the ADIN1200 and ADIN1300 Industrial Ethernet PHY features.

The ADIN1300 is the industry’s 10 Mbps/100 Mbps/1000 Mbps Industrial Ethernet PHY with excellent power, latency, and package size characteristics. Its EMC and ESD robustness has been extensively tested and can operate at ambient temperatures up to 105°C. The ADIN1300 PHY has been tested to EMC/ESD standards, as shown in Table 3. The cost and time associated with product compliance testing and certification can be significantly reduced by using Ethernet PHY technology that has been extensively tested to IEC and EN standards.

Figure 5. ADIN1200 with fido5200 for real-time multiprotocol Industrial Ethernet device connectivity.

Figure 6. ADIN1300 and ADIN1200 customer evaluation boards and software GUI.

The ADIN1200 Low Power 10 Mbps/100 Mbps Robust Industrial Ethernet PHY has undergone extensive EMC and ESD robustness testing and can operate at ambient temperatures up to 105°C. The ADIN1200 with fido5200 provides a system-level solution for multi-protocol, real-time industrial Ethernet device connectivity, supporting Profinet®, EtherNet/IP™, EtherCAT, Modbus TCP, and Powerlink for embedded dual-port device connectivity, as shown in Figure 5.

Supports Beckhoff EtherCAT and EtherCAT G Industrial Ethernet protocols

The ADIN1200 PHY meets all requirements of the EtherCAT Industrial Ethernet protocol and is included in the EtherCAT PHY Selection Guide. The ADIN1300 PHY meets all requirements of the EtherCAT G Industrial Ethernet protocol and is included in the EtherCAT G PHY Selection Guide. For more details, see Beckhoff’s Application Note – PHY Selection Guide.

Customer Support

Customer evaluation boards for the ADIN1300 and ADIN1200 are available, as well as a software GUI to speed evaluation. For video tutorials on the functionality of the application board software GUI, see the ADIN1300 and ADIN1200 product pages on analog.com. Figure 6 shows the application board and software GUI.

Summarize

To achieve seamless connection between IT and OT networks and realize the value of Industry 4.0, enhanced physical layer technology designed for industrial applications is a key design choice. Robust Industrial Ethernet PHY technology addresses power consumption, latency, solution size, 105°C ambient temperature, robustness (EMC/ESD), and long product lifetime, and is the foundation for enabling the connected factory. To address the challenges described in this article, Analog Devices recently introduced two new robust industrial Ethernet PHYs, the ADIN1300 (10 Mbps/100 Mbps/1000 Mbps) and the ADIN1200 (10 Mbps/100 Mbps/1000 Mbps)

About the Author

Maurice O’ Brien is the Strategic Marketing Manager for Analog Devices’ Industrial Connectivity Group. He is responsible for the strategy of enabling Industrial Ethernet connectivity solutions for industrial applications. Prior to that, Maurice worked for 15 years at Analog Devices in power management applications and marketing. He is a graduate of the University of Limerick, Ireland, with a bachelor’s degree in electrical engineering.

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