KSZ8895 Datasheet, PDF (113/115 Pages) Infineon Technologies AG – Integrated 5-Port 10/100 Managed Ethernet Switch with MII/RMII interface

Micrel, Inc.
KSZ8895MQ/RQ/FMQ
Selection of Isolation Transformer⁽¹⁾
One simple 1:1 isolation transformer is needed at the line interface. An isolation transformer with integrated common-
mode choke is recommended for exceeding FCC requirements at line side. Request to separate the center taps of
RX/TX at chip side. The following table gives recommended transformer characteristics.
Characteristics Name
Turns Ratio
Open-Circuit Inductance (min.)
Leakage Inductance (max.)
Inter-Winding Capacitance (max.)
D.C. Resistance (max.)
Insertion Loss (max.)
HIPOT (min.)
Value
1 CT : 1 CT
350µH
0.4µH
12pF
0.9Ω
1.0dB
1500Vrms
Test Condition
100mV, 100kHz, 8mA
1MHz (min.)
0MHz to 65MHz
Table 33. Transformer Selection Criteria
Note:
1.
2.
The IEEE 802.3u standard for 100BASE-TX assumes a transformer loss of 0.5dB. For the transmit line transformer, insertion loss of up to
1.3dB can be compensated by increasing the line drive current by means of reducing the ISET resistor value.
The center taps of RX and TX should be isolated for the low power consumption.
The following transformer vendors provide compatible magnetic parts for Micrel’s device:
Vendors and Parts
Pulse
YCL
TDK
LanKom
Datatronic
H1664NL
PH406082
TLA-6T718A
LF-H41S
NT79075
Auto
MDIX
Yes
Yes
Yes
Yes
Yes
Number
of Ports
4
4
1
1
1
Vendors and Parts
Pulse
Bel Fuse
YCL
Transpower
Delta
H1102
S558-5999-U7
PT163020
HB726
LF8505
Table 34. Qualified Magnetic Vendors
Auto
MDIX
Yes
Yes
Yes
Yes
Yes
Number of
Ports
1
1
1
1
1
Selection of Reference Crystal
Chacteristics
Frequency
Frequency tolerance (max)
Load capacitance (max)
Series resistance (max ESR)
Value
25.00000
<= ±50
27
40
Units
MHz
ppm
pF
Ω
Table 35. Typical Reference Crystal Characteristics
January 2011
113
M9999-012011-1.2