LXT9761/9781
Fast Ethernet 10/100 Multi-Port Transceiver with RMII
Datasheet
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.
Applications
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100BASE-T, 10/100-TX, or 100BASE-FX
Switches and multi-port NICs.
Product Features
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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
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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)
As of January 15, 2001, this document replaces the Level One document
LXT9761/9781 — Fast Ethernet 10/100 Multi-Port Transceiver with RMII.
Order Number: 249048-001
January 2001
