The LXT9781 is an eight-port PHY Fast Ethernet Transceiver that supports IEEE 802.3 physical layer applications at both 10 Mbps and 100 Mbps. It provides a Reduced Media Independent Interface (RMII) for switching and other independent port applications. The LXT9761 offers the same features and functionality in a six-port device. This data sheet uses the singular designation “LXT97x1” to refer to both devices.

All network ports provide a combination twisted-pair (TP) or pseudo-ECL (PECL) interface for a 10/100BASE-TX or 100BASE-FX connection.

The LXT97x1 provides three discrete LED driver outputs for each port, as well as eight global serial LED outputs. The device supports both half- and full-duplex operation at 10 Mbps and 100 Mbps, and requires only a single 3.3V power supply.

Product Features

■ Six or eight IEEE 802.3-compliant 10BASE-T or 100BASE-TX ports with integrated filters

■ 3.3V operation

■ Optimized for dual-high stacked R45 applications

■ Proprietary Optimal Signal Processing? architecture improves SNR by 3 dB over ideal analog filters

■ Robust baseline wander correction 100BASE-FX fiber-optic capability on all ports

■ Supports both auto-negotiation and legacy systems without auto-negotiation capability

■ JTAG boundary scan

■ Multiple Reduced MII (RMII) ports for independent PHY port operation

■ Configurable via MDIO port or external control pins.

■ Maskable interrupts

■ Low power consumption (390 mW per port, typical)

■ 208-pin PQFP (LXT9761 and LXT9781)

■ 272-pin PBGA (LXT9781 only)

Applications

■ 100BASE-T, 10/100-TX, or 100BASE-FX Switches and multi-port NICs.