General Description

The Realtek RTL8221B(I)-VB-CG (hereafter referred to as the RTL8221B(I)-VB, except where differences exist) is a highly integrated Ethernet PHY transceiver that is compatible with 10BASE-Te, 100BASE-TX, 1000BASE-T, and 2.5GBASE-T, and is fully compatible with both the IEEE 802.3 standard and the NBASE-T™ Alliance PHY. It provides all the necessary physical layer functions to transmit and receive Ethernet packets over CAT.5e UTP cable.

The RTL8221B(I)-VB uses state-of-the-art DSP technology and Analog Front End (AFE) to enable high-speed data transmission and reception over UTP cable. Functions such as Crossover Detection & Auto-Correction, polarity correction, MDI swap, adaptive equalization, cross-talk cancellation, echo cancellation, timing recovery, RFI protection, thermal management, loopback diagnostic capability, and error correction are implemented in the RTL8221B(I)-VB to provide robust transmission and reception capabilities.

Data transfer between MAC and PHY is via the SERDES (Serializer-Deserializer) interface, which supports SGMII, HiSGMII, and 2500Base-X. The RTL8221B(I)-VB operates at various digital I/O voltages, including 3.3V and 1.8V.


  • Compatible with IEEE 802.3, IEEE 802.3u, IEEE 802.3ab
  • Supports IEEE 802.3az (Energy Efficient Ethernet)
  • Supports IEEE 802.3bz (2.5GBASE-T)
  • Supports Full Duplex flow control (IEEE 802.3x)
  • Supports IEEE 802.3 optional ability (Energy Efficient Ethernet and Fast Retrain)
  • Integrated 10M BASE-Te and 100M/1000M/2.5GBASE-T IEEE 802.3 compatible transceiver
  • Supports 2.5G Lite (1G data rate) mode
  • Auto-Negotiation with Extended Next Page capability (XNP)
  • Compatible with NBASE-TTM Alliance PHY Specification
  • Supports pair swap/polarity/skew correction
  • Crossover Detection & Auto-Correction
  • Configurable MDI port ordering (MDI swap) for easy PCB layout
  • Supports hardware CRC (Cyclic Redundancy Check) function
  • Supports power down/link down power saving mode
  • Supports clause 22 and Clause 45 MDC/MDIO management interface
  • Supports rate adaptor for SerDes
  • Selectable SERDES interface to MAC control (SGMII/HiSGMII/2500 BASE-X)
  • Built-in Wake-on-LAN (WOL) over UTP
  • Supports Interrupt function over UTP
  • Supports Parallel Detection
  • Supports PHYRSTB core power Turn-Off
  • Baseline Wander Correction
  • Selectable 3.3/1.8V signaling for MMD access
  • Supports 25MHz crystal or external OSC
  • Provides 25MHz clock source for MAC
  • Provides 3 network customized LEDs with controllable LED Blinking Frequency and Duty Cycle
  • Self-Loopback diagnostic capability
  • Thermal management on PHY
  • 48-pin QFN Green Package
  • 22nm process with ultra-low power consumption
  • Complete hardware support for Synchronous Ethernet and Precision Time Protocol (PTP) including IEEE 1588v1, v2, and 802.1AS
  • Supports SPI Flash (up to 24MB flash size)
  • Industrial grade manufacturing process (RTL8221BI-VB/ RTL8221BI-VM)


  • DTV (Digital TV)
  • MAU (Media Access Unit)
  • CNR (Communication and Network Riser)
  • Game Console
  • Printer and Office Machine
  • DVD Player and Recorder
  • Ethernet Hub
  • Ethernet Switch
  • Base Stations and Controllers
  • Routers, DSLAMs, PON Equipment
  • Test and Measurement Systems
  • Industrial and Factory Automation Equipment
  • Multimedia synchronization and Real Time Networking