LAN8720A-CP-TR 10/100 Ethernet PHY for RMII Embedded Networking

ElecSuppliers ApplicationsAug 22, 2026

LAN8720A-CP-TR is a low-power 10BASE-T and 100BASE-TX Ethernet physical layer transceiver designed for embedded networking applications. It provides the physical Ethernet interface between a microcontroller or processor with an Ethernet MAC and the external network connection.

The device supports the reduced-pin-count RMII interface, allowing an Ethernet-enabled MCU to communicate with the PHY using fewer signal lines than a traditional MII connection. It supports 10 Mbps and 100 Mbps Ethernet operation and includes features such as auto-negotiation and HP Auto-MDIX.

LAN8720A-CP-TR Ethernet PHY

LAN8720A-CP-TR is a PHY rather than a complete Ethernet controller.

This distinction is important when designing an embedded Ethernet system.

A microcontroller with an integrated Ethernet MAC can handle Ethernet frame processing, while LAN8720A-CP-TR handles the physical-layer functions required to transmit and receive signals over an Ethernet cable.

A typical architecture therefore consists of an MCU with Ethernet MAC, the LAN8720A PHY, an Ethernet magnetics component and an RJ45 connector.

This division allows the main processor to handle networking software while the PHY handles the electrical Ethernet interface.

LAN8720A-CP-TR Specifications

LAN8720A-CP-TR supports 10BASE-T and 100BASE-TX operation and provides an RMII interface toward the Ethernet MAC.

The device uses a 24-pin QFN package measuring approximately 4 mm × 4 mm and supports a variable I/O voltage range from 1.6V to 3.6V. The commercial-temperature version is specified for 0°C to +85°C.

The device also integrates a 1.2V regulator and supports low-power operating modes, helping reduce the number of external power-management components in an embedded Ethernet design.

LAN8720A-CP-TR RMII Interface

RMII is one of the main reasons LAN8720A-CP-TR is popular in microcontroller-based Ethernet designs.

The reduced Media Independent Interface uses a narrower data path than traditional MII while supporting both 10 Mbps and 100 Mbps Ethernet.

The MAC and PHY exchange transmit and receive data through two-bit data paths, together with clock and control signals.

This reduces the number of PCB traces required between the MCU and PHY.

For compact embedded controllers, this can simplify PCB routing and leave more MCU pins available for other peripherals.

LAN8720A-CP-TR with STM32

Many STM32 microcontrollers include an Ethernet MAC but do not contain the complete physical-layer interface required to connect directly to an Ethernet cable.

LAN8720A-CP-TR can be paired with an STM32 Ethernet MAC through RMII.

The STM32 handles the Ethernet MAC functions and network software, while LAN8720A-CP-TR provides the physical Ethernet transceiver.

This architecture is useful for industrial controllers, networked measurement equipment, gateways and embedded servers.

When designing an STM32 and LAN8720A system, the RMII clock configuration should be decided early because the clock source and routing affect the overall Ethernet implementation.

LAN8720A-CP-TR 25MHz Crystal

A 25MHz reference is commonly associated with LAN8720A designs.

The PHY can use a 25MHz crystal to generate the required internal clocks and provide the RMII reference clock according to the selected clock configuration.

This can simplify the clock architecture because the Ethernet PHY does not necessarily require a separate high-frequency oscillator.

The crystal, load capacitors and associated traces should be placed according to the intended PHY reference-clock configuration.

Clock routing is particularly important because poor layout can lead to Ethernet initialization or link problems.

LAN8720A-CP-TR 50MHz RMII Clock

RMII requires a 50MHz reference clock for normal operation.

Depending on the system architecture, this clock can be generated by the PHY or supplied from another clock source.

This makes clock configuration one of the most important design decisions when connecting LAN8720A-CP-TR to an MCU.

A mismatch between the MCU clock configuration and PHY clock mode can result in a board that powers up correctly but fails to establish a reliable Ethernet link.

The clock source should therefore be defined at the schematic stage rather than left as a firmware configuration detail.

LAN8720A-CP-TR Auto-Negotiation

LAN8720A-CP-TR supports Ethernet auto-negotiation.

The PHY can negotiate the available communication speed and duplex mode with the connected Ethernet device.

This allows the interface to operate at either 10 Mbps or 100 Mbps according to the capabilities of the link partner.

For embedded products that may be connected to different network switches or routers, auto-negotiation can simplify deployment.

It also avoids requiring the user to manually configure the Ethernet speed in many standard applications.

LAN8720A-CP-TR Auto-MDIX

HP Auto-MDIX allows the Ethernet interface to automatically accommodate different cable wiring configurations.

This reduces the need to distinguish between straight-through and crossover Ethernet cables in applications where the feature is enabled.

For equipment designed for field installation, this can improve connection flexibility.

The feature is especially useful for embedded products that may be connected to a variety of network equipment without controlled cable selection.

LAN8720A-CP-TR Ethernet LEDs

LAN8720A-CP-TR provides status LED outputs that can be used to indicate Ethernet conditions.

Typical designs use LEDs to show link status, activity or other network states.

These indicators can be placed near the RJ45 connector, giving users a quick visual indication of whether the Ethernet connection is active.

For industrial equipment, status LEDs can also simplify troubleshooting during installation and maintenance.

LAN8720A-CP-TR Power Supply

The PHY can operate from a single 3.3V supply in common designs, while its flexible I/O supply architecture supports a wider voltage range.

The supply network should provide stable power with appropriate local bypass capacitors.

Because Ethernet signaling involves high-speed transitions, supply noise can affect overall interface performance.

The PHY power pins should therefore be connected with short, low-impedance paths and suitable decoupling.

The exact power arrangement should follow the selected LAN8720A operating mode and reference design.

LAN8720A-CP-TR Magnetics

LAN8720A-CP-TR does not replace the Ethernet isolation magnetics.

The PHY connects to the network through an appropriate transformer or integrated magnetics component.

The magnetics provide electrical isolation and interface the PHY's differential signals with the Ethernet cable.

The PHY-to-magnetics traces should be kept short and routed as controlled differential pairs where appropriate.

The magnetics and RJ45 connector should be positioned with the Ethernet signal path in mind rather than treating them as ordinary low-speed PCB components.

LAN8720A-CP-TR PCB Layout

Ethernet PCB layout requires careful attention to differential signaling and noise control.

The TX and RX differential pairs between the PHY and magnetics should be routed with appropriate impedance and matched as required by the design rules.

Unnecessary vias and sharp routing changes should be minimized.

The PHY should generally be positioned relatively close to the Ethernet magnetics to keep the analog differential path short.

The RMII signals between the MCU and PHY also require attention to clock and data timing.

Separating noisy switching power sections from the PHY and Ethernet signal paths can further improve system reliability.

LAN8720A-CP-TR Package

LAN8720A-CP-TR uses a compact 24-pin QFN package with an exposed thermal pad. The package is approximately 4 mm × 4 mm.

The small footprint is useful for embedded Ethernet products where PCB area is limited.

The exposed pad also needs to be handled correctly during PCB design and assembly.

For replacement work, engineers should verify the complete footprint, exposed-pad dimensions and pin assignment rather than relying only on the 24-pin package description.

LAN8720A-CP-TR Low-Power Features

LAN8720A-CP-TR includes multiple power-management features and low-power modes.

These functions can be useful for equipment that does not need the Ethernet interface to remain fully active all the time.

A networked device operating from a limited power budget can use low-power states when the Ethernet interface is inactive.

The system firmware should coordinate the PHY power state with the MCU's own power-management strategy.

LAN8720A-CP-TR Embedded Applications

LAN8720A-CP-TR can be used in many embedded Ethernet products.

Typical applications include industrial controllers, networked measurement instruments, embedded servers, printers, routers, gateways, digital video equipment, telecommunications equipment and network-enabled consumer electronics.

The device is particularly useful when the main processor already includes an Ethernet MAC and only an external PHY is required.

LAN8720A-CP-TR for Industrial Ethernet

Industrial controllers often need wired Ethernet for configuration, monitoring or communication with a supervisory system.

An MCU can run the application firmware and industrial communication stack while LAN8720A-CP-TR provides the physical Ethernet connection.

For an industrial product, the PHY is only one part of the complete interface.

The PCB should also consider ESD protection, surge conditions, isolation, grounding, connector selection and the environmental requirements of the finished equipment.

LAN8720A-CP-TR for IoT Gateways

Although wireless connectivity is common in IoT products, wired Ethernet remains important for gateways, fixed controllers and infrastructure devices.

LAN8720A-CP-TR can provide a compact 10/100 Ethernet interface for an IoT gateway based on an Ethernet-capable MCU or processor.

The gateway can collect data from local sensors and send it to a network server through the Ethernet connection.

Compared with a wireless-only architecture, wired Ethernet can provide predictable physical connectivity for equipment installed in fixed locations.

LAN8720A-CP-TR Replacement

When selecting a LAN8720A-CP-TR replacement, the first parameters to compare are Ethernet speed, interface type and package.

A suitable replacement should support 10BASE-T and 100BASE-TX if the original application requires both speeds.

RMII compatibility is also essential when the existing MCU is connected through the reduced-pin-count interface.

Other important parameters include supply voltage, clock configuration, PHY address, LED functions, temperature range and differential-interface characteristics.

A PHY with a similar name is not necessarily a drop-in replacement.

LAN8720A-CP-TR Alternative

An alternative Ethernet PHY may be considered when a design requires additional features such as Gigabit Ethernet, a wider temperature range or different host interfaces.

For a compact 10/100 embedded controller, however, a low-pin-count RMII PHY can remain an efficient solution.

When selecting another PHY, designers should also consider software compatibility.

The MAC may communicate with the PHY through the management interface, so differences in PHY registers or initialization procedures can require firmware changes.

LAN8720A-CP-TR vs Ethernet Controller

LAN8720A-CP-TR should not be confused with an Ethernet controller.

An Ethernet controller normally handles higher-level MAC functions and may provide a host interface such as SPI or PCIe.

LAN8720A-CP-TR is a physical-layer transceiver.

If the selected MCU does not contain an Ethernet MAC, simply adding LAN8720A-CP-TR will not create a complete Ethernet solution.

The system architecture must therefore include both the required MAC functionality and the PHY.

Choosing LAN8720A-CP-TR

LAN8720A-CP-TR is a compact solution for adding 10/100 Mbps wired Ethernet to an embedded system with an RMII-capable MAC.

Its combination of RMII support, auto-negotiation, Auto-MDIX, flexible I/O voltage and compact QFN packaging makes it suitable for many network-connected embedded products.

For a new design, the most important points are the RMII clock architecture, PHY address, magnetics, differential-pair layout, power supply and Ethernet protection.

For a replacement project, engineers should verify the package, pinout, clock modes and PHY register behavior before selecting an alternative.