LXT974

The LXT974 and LXT975 are four-port PHY Fast Ethernet Transceivers which support IEEE 802.3 physical layer applications at both 10 Mbps and 100 Mbps. They provide all of the active circuitry to interface four 802.3 Media Independent Interface (MII) compliant controllers to 10BASE-T and/or 100BASE-TX media.

This data sheet applies to all versions of the LXT974 and LXT975 products including LXT974A, LXT974B, LXT975A, and LXT975B. As a result of product changes, Revision 4 parts are labeled LXT974B and LXT975B. Revision 3 parts are labeled LXT974A and LXT975A. The differences in these product revisions are described in the LXT 974/975 Specification Update.

All four ports on the LXT974 provide a combination twisted-pair (TP) or pseudo-ECL (PECL) interface for a 0/100BASE-TX or 100BASE-FX connection.

The LXT975 is pin compatible with the LXT974 except for the network ports. The LXT975 is optimized for dual-high stacked RJ-45 modular applications and provides a twisted-pair interface on every port, but the PECL interface on only two.

The LXT974/975 provides three separate LED drivers for each of the four PHY ports and a serial LED interface. In addition to standard Ethernet, each chip supports full- duplex operation at 10 Mbps and 100 Mbps. The LXT 974/975 requires only a single 5V power supply. The MII may be operated independently with either a 3.3V or 5V supply.