FLLXT971A Intel, FLLXT971A Datasheet - Page 52

• Manufacturer Part Number: FLLXT971A
• Description: 3.3V Dual Speed Fast Ethernet PHY Transceicer
• Manufacturer: Intel

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LXT971A 3.3V Dual-Speed Fast Ethernet Transceiver
4.3
52
The Fiber Interface
The fiber interface consists of an LVPECL transmit and receive pair to an external fiber-optic
transceiver. Both 3.3 V fiber-optic transceivers and 5 V fiber-optic transceivers can be used with
the LXT971A.
The following should occur in 3.3 V fiber transceiver applications as shown in
Refer to the fiber transceiver manufacturer’s recommendations for termination circuitry.
shows a typical example of an LXT971A-to-3.3 V fiber transceiver interface.
The following occurs in 5 V fiber transceiver applications as shown in
The signal detect pin on a 5 V fiber transceiver interface should use the logic translator circuitry as
shown in
circuitry.
while
•
•
•
•
•
The transmit pair should be DC-coupled with the 50 Ω/16 Ω pull-up combination
The receive pair should be DC-coupled with an emitter current path for the fiber transceiver
The signal detect pin should be DC-coupled with an emitter current path for the fiber
transceiver
The transmit pair should be AC-coupled and re-biased to 5 V PECL input levels
The receive pair should be AC-coupled with an emitter current path for the fiber transceiver
and re-biased to 3.3 V LVPECL input levels.
Figure 27
Figure
Figure 26
shows the interface circuitry for the logic translator.
27. Refer to the fiber transceiver manufacturer’s recommendations for termination
shows a typical example of an LXT971A-to-5 V fiber transceiver interface,
Figure
Rev. Date: August 7, 2002
26:
Figure
Document #: 249414
Revision #: 002
25:
Datasheet
Figure 25