Essential Components for Designing Single Pair Ethernet Applications

The global Industrial IoT (IIoT) market is projected to grow at a double-digit rate annually to $59.6 billion by 2029 as manufacturers and solution providers seek to connect more and more machines and sensors to the internet in pursuit of greater automation, real-time monitoring, and data collection. Single pair Ethernet (SPE) technology provides product designers with new opportunities to exploit that demand for applications such as sensors, actuators, cameras, displays, controllers, gateways, and switches.

The task force that developed the IEEE 802.3cg standard for 10 Mb/s SPE was focused on addressing the "Ethernet Gap" at the edge in industrial networking. That's where non-Ethernet fieldbuses dominate automation network connections due to being generally more economical and simpler to install, less sensitive to noise, and easier to transmit power over the network, among other factors.

Unlike conventional Ethernet, which uses four pairs of twisted conductors, SPE uses a single pair to transmit data at 10 Mbps over distances as much as 1,000 meters for industrial applications using 10Base-T1L. SPE can be combined with Single Pair Power over Ethernet (SPoE) to simultaneously deliver power to and transmit data to and from IIoT devices.

SPE and SPoE bring industrial automation the benefits of a common physical layer (PHY), standardized network interface cards (NICs), and greater flexibility for vendors developing devices to interact and communicate over Ethernet. The ability to convey both data and power over longer distances makes it easier to communicate with devices, as well as alleviates the need for batteries in sensors and other devices.

SPE provides solution designers and customers with advantages that include reduced weight and cost of cabling, compatibility with existing Ethernet infrastructure, and greater flexibility in extending that industry-standard technology. The challenges in designing SPE applications include overcoming electromagnetic interference, signal integrity, power delivery, and thermal management issues.

Components required for SPE applications

Designing 10Base-T1L SPE applications requires a mix of components that combine to ensure the integrity of power and data, isolation, and noise filtering, including common-mode chokes (CMCs), differential mode inductors (DMIs), and isolated coupled inductors. TDK is the first supplier to offer all the inductors needed to implement industrial SPE with and without power transmission.

If planning to use 10Base-T1L for data transmission only between control and sensing or acting elements, designers can utilize just the CMC, which filters out noise. TDK's RCM70CGI-471 (Figure 1) suppresses asymmetrical interference coupled in on lines while data signals are unaffected. It operates over a temperature range from -40 to +125°C, with a rated voltage of 80 VDC.

Figure 1: TDK's RCM70CGI common mode choke for interference suppression. (Image source: TDK)

For power over data line (PoDL) applications, designers will need to also include a differential mode inductor, such as TDK's PID75-650M (Figure 2) to reduce impedance and ensure the integrity of power transmission. It has a rated inductance value of 2 x 65 μH, low DC resistance, and operates in temperatures up to +150°C.

Figure 2: TDK's PID75-650M differential mode inductor reduces impedance and ensures power transmission integrity. (Image source: TKD)

In the case of implementations where safety is critical and galvanic isolation is required, designers will need to complement the CMC and DMI with an isolating coupled inductor to prevent undesired current flowing between devices. TDK's ICI70CGI-222 (Figure 3) has a rated inductance of 2.2 mH, stray capacitance of less than 20 pF, and voltage strength up to 2250 VDC.

Figure 3: The ICI70CGI isolation inductor. (Image source: TDK)

Conclusion

TDK's industrial SPE inductors enable product designers to create SPE devices for applications in factory automation, building automation, transportation, energy, and healthcare. With support for communication protocols, including IEEE 802.3cg, IEEE 802.3bu, and IEEE 802.3bw, SPE applications can extend Ethernet infrastructure with greater flexibility, reduced cabling costs, and decreased weight.