LAN8720 Module

LAN8720 Ethernet Communication Module

10 / 100 RMII Internet Transceiver Communication Network Module

     The LAN8720 Module is a 10/100Mbps Ethernet physical layer (PHY) transceiver board based on the Microchip LAN8720 chip. It connects over the RMII interface to a microcontroller that has an Ethernet MAC (such as ESP32, STM32F4/F7/H7) and gives it a wired network connection through an RJ45 socket. RMII needs fewer pins than MII; on this board 9 signal pins are enough for data, clock and management lines.

     The board runs from a single 3.3V supply; the 1.2V regulator inside the chip generates the core voltage itself. The on-board 50MHz oscillator provides the RMII reference clock, which is also passed to the microcontroller through the nINT/REFCLK pin. Thanks to HP Auto-MDIX, straight or crossover Ethernet cables both work. The 24-pin 4mm x 4mm QFN chip, RJ45 socket and 12-pin right-angle header sit on a small board of about 56mm x 27mm weighing 13gr.

     This board is a PHY, not a stand-alone Ethernet controller: the TCP/IP stack and the MAC run on the microcontroller it is connected to. Therefore it cannot be used (over SPI) with boards that have no Ethernet MAC; those boards need an SPI Ethernet module such as W5500 or ENC28J60.

Key features:

     Few pins with RMII: Connects to the Ethernet MAC of the microcontroller with the TX0, TX1, TX_EN, RX0, RX1, CRS data lines, the MDIO/MDC management lines and the nINT/REFCLK clock line; the pin count is half that of MII.

     50MHz clock on board: The 50MHz reference clock required by RMII comes from the on-board oscillator. The NC pin of the header is unconnected on the board; if the oscillator enable is wired to this pin with a short soldered wire, the clock can be started after the microcontroller has booted.

     Single 3.3V supply: Thanks to the integrated 1.2V regulator no separate core supply is needed; the I/O voltage range is 1.6V - 3.6V.

     Auto-MDIX: Detects the cable direction itself; connects to a switch, modem or directly to a computer with a straight cable.

     Small and light: With a 55.75mm x 26.80mm board and 13gr weight it fits easily into device enclosures.

Features:

• Product type: 10/100Mbps Ethernet physical layer (PHY) transceiver module
• Model: LAN8720 Module (LAN8720 ETH Board)
• Chip: Microchip LAN8720, 24-pin QFN (4mm x 4mm), lead-free, RoHS compliant
• Ethernet speed: 10BASE-T / 100BASE-TX (10/100Mbps)
• Microcontroller interface: RMII (Reduced Media Independent Interface)
• Management interface: MDIO / MDC (SMI)
• Supply: single 3.3V
• I/O voltage range: 1.6V - 3.6V
• Internal regulator: integrated 1.2V core regulator
• Cable detection: HP Auto-MDIX (straight and crossover cable)
• Clock source: on-board 50MHz oscillator; 50MHz reference clock on the nINT/REFCLK pin
• Power management: flexible power management architecture
• Header pins (12 pins, 2 x 6, 90 degree right-angle): TX1, TX_EN, TX0, RX0, RX1, nINT/REFCLK (printed nINT/RETCLK on the board), CRS, MDIO, MDC, VCC, GND, NC (unconnected)
• Network connector: RJ45 Ethernet socket with status LEDs
• PoE: not supported
• Colour: Black PCB, white silkscreen
• Dimensions: 55.75mm x 26.80mm (about 56mm x 27mm)
• Weight: 13gr

Usage information:

• Connect the VCC pin to 3.3V and GND to the microcontroller GND. Connect the TX0, TX1, TX_EN, RX0, RX1, CRS lines to the RMII pins of the microcontroller, MDIO and MDC to the management pins and nINT/REFCLK to the RMII clock input. Keep the wires as short as possible.
• With ESP32 the 50MHz clock goes into GPIO0. Because GPIO0 selects the boot mode at power-up, the ESP32 may enter download mode if the oscillator runs during boot; as a fix, solder the oscillator enable to the unconnected NC pin with a short wire (board modification), connect the NC pin to a GPIO, pull it to GND with 4.7kΩ and enable the oscillator in software after boot. Without this modification the board may start unreliably with ESP32.
• In software select LAN8720 as PHY type and enter the PHY address and the MDC/MDIO pins. ESP-IDF, the Arduino ESP32 core (ETH library), ESPHome and STM32Cube LwIP examples support LAN8720.

Application areas:

•  Adding wired Ethernet to ESP32 and STM32 boards
•  Modbus TCP devices and sensor reading over the network
•  IoT nodes sending data with MQTT
•  Embedded web server and network-managed device panels
•  Wired connection instead of Wi-Fi for home automation (ESPHome, Tasmota)
•  Data acquisition and network logging systems
•  Remote monitoring and control devices
•  Serial port - Ethernet converter and gateway applications
•  Network connection in panels and machine rooms where Wi-Fi is weak

Precautions:

•  This module only works with microcontrollers that have Ethernet MAC hardware (such as ESP32, STM32F4/F7/H7). It does not connect over SPI; on boards without a MAC such as Arduino Uno use a W5500 or ENC28J60 module.
•  The supply is 3.3V. Do not apply 5V to the VCC pin; the data pins are also 3.3V level.
•  The RMII clock line is 50MHz; with long jumper wires the signal degrades and the link drops. Keep the wires short or place the module close to the main board.
•  PoE is not supported. Do not use a switch port that supplies PoE voltage to the RJ45 socket.

Package contents:

•  1 Piece LAN8720 Module
•  1 Piece 12-pin (2 x 6) 90 degree right-angle male header ( Assembled )
•  Note: Ethernet cable and jumper wires are not included in the package.