Intel
®
LXT9785 and Intel
®
LXT9785E
Advanced 8-Port 10/100 Mbps PHY
Transceivers
Datasheet
The Intel
®
LXT9785 and Intel
®
LXT9785E are 8-port Fast Ethernet PHY Transceivers
supporting IEEE 802.3 physical layer applications at 10 Mbps and 100 Mbps. These devices
provide Serial/Source Synchronous Serial Media Independent Interfaces (SMII/SS-SMII) and
Reduced Media Independent Interface (RMII) for switching and other independent port
applications. The LXT9785 and LXT9785E are identical except for the IP telephony features
included in the LXT9785E transceiver. The LXT9785E is an enhanced version of the LXT9785
that detects Data Terminal Equipment (DTE) requiring power from the switch over a CAT5
cable. The system uses the information collected by the LXT97985E to apply power if the DTE
at the far end requires power over the cable, such as an IP telephone.
Each network port can provide a twisted-pair (TP) or Low-Voltage Positive Emitter Coupled
Logic (LVPECL) interface. The twisted-pair interface supports 10 Mbps and 100 Mbps
(10BASE-T and 100BASE-TX) Ethernet over twisted-pair. The LVPECL interface supports
100 Mbps (100BASE-FX) Ethernet over fiber-optic media.
The LXT9785/LXT9785E provides three discrete LED driver outputs for each port. The devices
support both half-duplex and full-duplex operation at 10 Mbps and 100 Mbps and require only a
single 2.5 V power supply.
Applications
Enterprise switches
IP telephony switches
Storage Area Networks
Multi-port Network Interface Cards (NICs)
Product Features
Eight IEEE 802.3-compliant 10BASE-T or
100BASE-TX ports with integrated filters.
100BASE-FX fiber-optic capability on all
ports.
2.5 V operation.
Low power consumption; 250 mW per port
typical.
Multiple RMII or SMII/SS-SMII ports for
independent PHY port operation.
Auto MDI/MDIX crossover capability.
Proprietary Optimal Signal Processing™
architecture improves SNR by 3 dB over
ideal analog filters.
Optimized for dual-high stacked RJ-45
applications.
MDIO sectionalization into 2x4 or 1x8
configurations.
Supports both auto-negotiation systems and
legacy systems without auto-negotiation
capability.
Robust baseline wander correction.
Configurable through the MDIO port or
external control pins.
JTAG boundary scan.
208-pin PQFP: LXT9785HC,
LXT9785EHC, LXT9785HE.
241-ball BGA: LXT9785BC,
LXT9785EBC.
196-ball BGA: LXT9785MBC
DTE detection for remote powering
applications (LXT9785E only).
Extended temperature operation of -40
o
C to
+85
o
C (LXT9785HE).
Document Number: 249241
Revision Number: 007
Revision Date: August 28, 2003
INTEL [ INTEL CORPORATION ]
