Simplify Ethernet to the Edge With 10BASE-T1S PMD Transceivers

Ethernet to the Edge

As designers continue seeking ways to reduce complexity, all-Ethernet systems are gaining traction due to their ability to reduce wiring requirements and minimize the need for protocol translations. A key part of this approach is extending Ethernet to the edge to connect sensors and actuators, a role traditionally handled by proprietary or specialized buses. Ethernet serves as the backbone for many systems and, with 10BASE-T1S, helps extend connectivity to edge devices while reducing gateways and overall system complexity through multidrop functionality. As a result, systems designers are increasingly adopting this architecture.

To effectively extend Ethernet to the edge of a network, simplicity is important, driving demand for a new type of 10BASE-T1S transceiver similar to a CAN transceiver. To address this need, the 10BASE-T1S PMD transceiver with an OA3P interface was developed, providing a straightforward design with minimal pin requirements to help maintain simplicity at the edge.

What Is a PMD Transceiver?

Physical Medium Dependent (PMD) transceivers split the functions of a traditional 10BASE-T1S transceiver into two parts, where the digital functionality is offloaded to the host controller while the PMD transceiver handles the essential analog physical layer functions. This split provides a simple, low-cost, small-footprint transceiver for simplified Ethernet extension to edge devices. These 10BASE-T1S devices enable flexibility in edge designs through the Open Alliance 3-pin (OA3p) interface, which allows connection to MCUs using minimal pins. The smaller form factor can help reduce costs and overall design complexity, while the standardized interface helps simplify interoperability across edge designs. 10BASE-T1S PMD transceivers provide a compact, low-power approach to native Ethernet edge connectivity.

Bus Comparison Chart

CAN/CAN FD and RS-485 have long served as go-to technologies for reliable edge connectivity. With the introduction of 10BASE-T1S, designers can extend Ethernet to edge devices while reducing or eliminating gateways. Unlike traditional point-to-point Ethernet, 10BASE-T1S supports multidrop topology, where multiple edge nodes can share the same bus line to help reduce cabling weight and complexity. Physical Layer Collison Avoidance (PLCA) coordinates access to the shared bus to help avoid collisions and improve network efficiency through increased bandwidth utilization.

The 10BASE-T1S PMD transceivers combine CAN-like simplicity with standardized Ethernet communication, making them a practical solution for designers transitioning from specialized buses to all-Ethernet architectures. By using an OA3P interface instead of a higher-pin-count interface, PMD transceivers reduce the interface requirements on the MCU and the overall power consumption. Together, this enables a simplified transceiver design for distributed edge nodes where deployment of traditional Ethernet could introduce additional complexity.

SBC Functionality

The System Basis Chip (SBC) functionality usually found in CAN/LIN can also be implemented in PMD transceivers, bringing advanced fail-safe functionality and reduced power consumption to these devices. With an SBC, a watchdog ensures the MCU is functioning as expected by setting a timer. If the MCU does not refresh or respond to the timer before it expires, the SBC can reset the MCU, power-cycle part of the system or trigger a fault indication to help recover Ethernet communication. This functionality is particularly important for safety-critical applications where a frozen or otherwise incapacitated MCU could interrupt communications, resulting in lost sensor data or unresponsive actuators. By supporting automatic recovery without human intervention, this watchdog fail-safe helps improve overall system reliability.

SBCs also offer integrated power management through voltage regulators, power sequencing, sleep/wake controls and brownout detection, all which help make the node more self-sufficient. Thermal and voltage protection are also integrated into the SBC. Coordinated fault handling allows the SBC to respond to faults through a centralized fault-management function rather than through isolated subsystem reactions.

In a failure scenario, many SBCs offer a "limp home" fail-safe mode, a special operating state that allows users to safely reach a service location. This is particularly important in vehicles, where preventing a sudden loss of functionality can help protect passengers. Limp home operation may include maintaining minimal communications across the system, disabling non-critical loads or reducing power consumption. The SBC can also signal to the rest of the system and to the user, for example through a warning light, that something has entered a degraded operating state and requires transition to a defined safe state.

Our PMD Offerings

We offer the LAN8679, a 10BASE-T1S PMD transceiver with OA3P interfaces, and the LAN8680, which offers SBC functionality. Both offer enhanced Electromagnetic Compatibility (EMC) and Electromagnetic Interference (EMI) performance, are qualified to ISO26262 and AEC-Q100 standards and are configured in small-footprint packages (8-pin/16-pin VDFN, respectively).

Additionally, the LAN8660X/1X/2X 10BASE-T1S endpoints with standards-based Remote Control Protocol (RCP) include an integrated PMD transceiver for a space-saving single-chip edge solution. Offering specialized solutions for control, lighting and audio, and with ISO 26262 and AEC-Q100 qualifications, these endpoints are equipped to fit a variety of design requirements.

The Future for PMD Transceivers

With their compact footprint, low power consumption and simplified MCU connectivity through the OA3P interface, PMD transceivers provide an efficient, standardized solution for distributed edge nodes. As network architectures continue to shift towards centralized zonal and software-defined models, demand for simple Ethernet edge connectivity is expected to continue growing. With the availability of these 10BASE-T1S PMD devices, adoption of Single Pair Ethernet (SPE) at the edge is likely to accelerate across a wide range of applications.

Want More?

For more information about our PMD transceivers and other 10BASE-T1S offerings, please visit our 10BASE-T1S Ethernet Products web page.