Datasheet

 2016 Microchip Technology Inc. DS00002246A-page 101
KSZ8895MQX/RQX/FQX/MLX
9.0 SELECTION OF ISOLATION TRANSFORMER, (Note 9-1)
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. Table 9-1 gives recommended transformer characteristics.
Note 9-1 The IEEE 802.3u standard for 100BASE-TX assumes a transformer loss of 0.5 dB. For the transmit
line transformer, insertion loss of up to 1.3 dB can be compensated by increasing the line drive
current by means of reducing the ISET resistor value.
9.0.1 SELECTION OF TRANSFORMER VENDORS
The following transformer vendors provide compatible magnetic parts for the KSZ8895MQX/RQX/FQX/MLX:
9.0.2 SELECTION OF REFERENCE CRYSTAL
TABLE 9-1: TRANSFORMER SELECTION CRITERIA
Characteristics Value Test Condition
Turns Ratio 1 CT:1 CT —
Open-Circuit Inductance (min.) 350 µH 100 mV, 100 kHz, 8 mA
Insertion Loss (max.) 1.1 dB 0.1 MHz to 100 MHz
HIPOT (min.) 1500 V
RMS
—
TABLE 9-2: QUALIFIED MAGNETIC VENDORS
Vendor and Part
Auto
MDIX
Number of
Ports
Vendor and Part
Auto
MDIX
Number of
Ports
Pulse H1664NL Yes 4 Pulse H1102 Yes 1
Pulse H1164NL 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 9-3: TYPICAL REFERENCE CRYSTAL CHARACTERISTICS
Characteristics Value
Frequency 25.00000 MHz
Frequency Tolerance (max.)  ±50 ppm
Load Capacitance (max.) 27 pF
Series Resistance (ESR) 40