Intel® LXT9785 and LXT9785E Advanced
8-Port 10/100 Mbps PHY Transceivers
Datasheet
The Intel® LXT9785 and 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 LXT9785E 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
Storage Area Networks
IP telephony switches
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.
Supports both auto-negotiation systems and
legacy systems without auto-negotiation
capability.
Robust baseline wander correction.
2.5 V operation.
Low power consumption; 250 mW per port
typical.
Configurable through the MDIO port or
external control pins.
JTAG boundary scan.
Multiple RMII or SMII/SS-SMII ports for
independent PHY port operation.
208-pin PQFP: LXT9785HC,
LXT9785EHC, LXT9785HE.
Auto MDI/MDIX crossover capability.
241-ball BGA: LXT9785BC,
LXT9785EBC.
196-ball BGA: LXT9785MBC (includes
DTE detection similar to the LXT9785E)
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.
DTE detection for remote powering
applications (LXT9785E and
LXT9785MBC only).
o
Extended temperature operation of -40 C
o
to +85 C (LXT9785E only).
Document Number: 249241
Revision Number: 009
Revision Date: April 30, 2004