
LXT980/980A Dual-Speed, 5-Port Fast Ethernet Repeater
Datasheet
51
3.1.8
Magnetics Information
The LXT980 requires a 1:1 ratio for the receive transformers and a 2:1 ratio for the 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 23
for transformer specifications
and
Magnetic Manufacturers for Networking Product Applications
(App. Note 73) for a reference
list of compatible magnetic components. Before committing to a specific component, designers
should test and validate the magnetics in the specific application to verify that system requirements
are met.
Table 23. Magnetics Specifications
Parameter
Min
Nom
Max
Units
Test Condition
Rx turns ratio
–
1 : 1
–
–
Tx turns ratio
–
2 : 1
–
–
Insertion loss
0.0
–
1.1
dB
80 MHz
Primary inductance
350
–
–
μ
H
Transformer isolation
–
2
–
kV
Differential to common mode rejection
–
–
-40
dB
.1 to 60 MHz
–
–
-35
dB
60 to 100 MHz
Return Loss - standard
–
–
-16
dB
30 MHz
–
–
-10
dB
80 MHz
Return Loss - improved
–
–
-20
dB
30 MHz
–
–
-15
dB
80 MHz