Specifications

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 Value Test Condition
Turns Ratio 1 CT : 1 CT
Open-Circuit Inductance (min.) 350µH 100mV, 100kHz, 8mA
Insertion Loss (max.) 1.1dB 0.1MHz to 100MHz
HIPOT (min.) 1500Vrms
Table 33. Transformer Selection Criteria
Notes:
1. 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.
2. 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
Auto
MDIX
Number
of Ports
Vendors and Parts
Auto
MDIX
Number of
Ports
Pulse H1664NL Yes 4 Pulse H1102 Yes 1
YCL PH406082 Yes 4 Bel Fuse S558-5999-U7 Yes 1
TDK TLA-6T718A Yes 1 YCL PT163020 Yes 1
LanKom LF-H41S Yes 1 Transpower HB726 Yes 1
Datatronic NT79075 Yes 1 Delta LF8505 Yes 1
Table 34. Qualified Magnetic Vendors
Selection of Reference Crystal
Chacteristics Value Units
Frequency 25.00000 MHz
Frequency tolerance (max)
<= ±50
ppm
Load capacitance (max) 27 pF
Series resistance (max ESR) 40
Ω
Table 35. Typical Reference Crystal Characteristics
March 12, 2014
117
Revision 1.7