
Micrel, Inc.
KSZ8873MLL/FLL/RLL
September 20, 2013
113
Revision 1.6
Selection of Isolation Transformers
A 1:1 isolation transformer is required at the line interface. An isolation transformer with integrated common-mode choke
is recommended for exceeding FCC requirements.
Table 33 gives recommended transformer characteristics.
Table 33. Transformer Selection Criteria
Parameter
Value
Test Condition
Turns Ratio
1 CT : 1 CT
Open-Circuit Inductance (minimum)
350H
100mV, 100kHz, 8mA
Leakage Inductance (maximum)
0.4H
1MHz (minimum)
Inter-Winding Capacitance (maximum)
12pF
D.C. Resistance (maximum)
0.9
Insertion Loss (maximum)
1.0dB
0MHz – 65MHz
HIPOT (minimum)
1500Vrms
Table 34. Qualified Single-Port Magnetics
Magnetic Manufacturer
Part Number
Auto MDI-X
Number of Port
Bel Fuse
S558-5999-U7
Yes
1
Bel Fuse (MagJack)
SI-46001
Yes
1
Bel Fuse (MagJack)
SI-50170
Yes
1
Delta
LF8505
Yes
1
LanKom
LF-H41S
Yes
1
Pulse
H1102
Yes
1
Pulse (low cost)
H1260
Yes
1
Datatronic
NT79075
Yes
1
Transpower
HB726
Yes
1
YCL
LF-H41S
Yes
1
TDK (Mag Jack)
TLA-6T718
Yes
1
Selection of Reference Crystal
Table 35. Typical Reference Crystal Characteristics
Chacteristics
Value
Units
Frequency
25.00000
MHz
Frequency Tolerance (maximum)
±50
ppm
Load capacitance (maximum)
20
pF
Series Resistance
40