KSZ8081 Physical-Layer Transceivers

By Microchip Technology 74

KSZ8081 Physical-Layer Transceivers

The Microchip KSZ8081 is a single-supply 10Base-T/100Base-TX Ethernet physical-layer transceiver for transmission and reception of data over standard CAT-5 unshielded twisted pair (UTP) cable. It is a highly-integrated PHY solution that reduces board cost and simplifies board layout by using on-chip termination resistors for the differential pairs and by integrating a low-noise regulator to supply the 1.2 V core.

It offers the Media Independent Interface (MII) and the KSZ8081RNB offers the Reduced Media Independent Interface (RMII) for direct connection with MII/RMII-compliant Ethernet MAC processors and switches. A 25 MHz crystal is used to generate all required clocks, including the 50 MHz RMII reference clock output for the KSZ8081RNB.

The KSZ8081 provides diagnostic features to facilitate system bring-up and debugging in production testing and product deployment. Parametric NAND tree support enables fault detection between KSZ8081 I/Os and the board. Microchip LinkMD® TDR-based cable diagnostics identify faulty copper cabling. The KSZ8081MNX and KSZ8081RNB are available in 32-pin, lead-free QFN packages.


  • Single-chip 10Base-T/100Base-TX IEEE 802.3-compliant Ethernet transceiver
  • MII interface support (KSZ8081MNX)
  • RMII v1.2 interface support with a 50 MHz reference clock output to MAC, and an option to input a 50 MHz reference clock (KSZ8081RNB)
  • Back-to-back mode support for a 100 Mbps copper repeater
  • MDC/MDIO management interface for PHY register configuration
  • Programmable interrupt output
  • LED outputs for link, activity, and speed status indication
  • On-chip termination resistors for the differential pairs
  • Baseline wander correction
  • HP Auto MDI/MDI-X to reliably detect and correct straight-through and crossover cable connections with disable and enable option
  • Auto-negotiation to automatically select the highest linkup speed (10/100 Mbps) and duplex (half/full)
  • Power-down and power-saving modes
  • LinkMD® TDR-based cable diagnostics to identify faulty copper cabling
  • Parametric NAND Tree support for fault detection between chip I/Os and the board
  • Loopback modes for diagnostics
  • Single 3.3 V power supply with VDD I/O options for 1.8 V, 2.5 V, or 3.3 V
  • Built-in 1.2 V regulator for core
  • Available in 32-pin (5 mm x 5 mm) QFN package


  • IP camera
  • OTT
    • Industrial
      • Game console
      • IP phone
      • IP set-top box
      • IP TV
      • MFP