LXT971A 3.3V Dual-Speed Fast Ethernet Transceiver
4.0
Application Information
4.1
Magnetics Information
The LXT971A requires a 1:1 ratio for both the receive and transmit transformers. The transformer
isolation voltage should be rated at 2 kV to protect the circuitry from static voltages across the
connectors and cables. Refer to Table 15 for transformer requirements.
A cross-reference list of magnetic manufacturers and part numbers is available in Magnetic
Manufacturers for Networking Product Applications (document number 248991) and is found on
the Intel web site (www.Intel.com). Before committing to a specific component, contact the
manufacturer for current product specifications and validate the magnetics for the specific
application.
Table 15. Magnetics Requirements
Parameter
Min
Nom
Max
Units
Test Condition
Rx turns ratio
–
–
1 : 1
1 : 1
0.6
–
–
–
–
–
Tx turns ratio
–
–
Insertion loss
0.0
350
–
1.1
–
dB
µH
kV
dB
dB
dB
dB
–
–
Primary inductance
Transformer isolation
1.5
–
–
–
40
35
-16
-10
–
.1 to 60 MHz
60 to 100 MHz
30 MHz
80 MHz
Differential to common mode rejection
Return Loss
–
–
–
–
–
–
4.2
Typical Twisted-Pair Interface
Table 16 provides a comparison of the RJ-45 connections for NIC and Switch applications in a
typical twisted-pair interface setting.
Table 16. I/O Pin Comparison of NIC and Switch RJ-45 Setups
RJ-45
Symbol
Switch
NIC
TPIP
TPIN
1
2
3
6
3
6
1
2
TPOP
TPON
Figure 22 on page 49 shows a typical twisted-pair interface with the RJ-45 connections crossed
over for a Switch configuration. Figure 23 on page 50 provides a typical twisted-pair interface with
the RJ-45 connections configured for a NIC application.
48
Datasheet
Document #: 249414
Revision #: 002
Rev. Date: August 7, 2002
INTEL [ INTEL ]
