Datasheet

 2016-2017 Microchip Technology Inc. DS00002112B-page 127
KSZ8795CLX
9.0 SELECTION OF ISOLATION TRANSFORMER
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 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. Tabl e 9 - 1 gives recommended transformer characteristics.
Table 9-2 lists the transformer vendors that provide compatible magnetic parts for this device.
10.0 SELECTION OF REFERENCE CRYSTAL
Table 10-1 lists the typical reference crystal characteristics for this device.
Note 10-1 Typical value varies per specific crystal specs.
TABLE 9-1: 25 MHZ CRYSTAL/REFERENCE CLOCK 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
Vendors and Parts Auto MDIX
Number
of Ports
Vendors and Parts Auto MDIX
Number
of Ports
Pulse H1164NL 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 10-1: TYPICAL REFERENCE CRYSTAL CHARACTERISTICS
Characteristics Value
Frequency 25.00000 MHz
Frequency Tolerance (max.)  ±50 ppm
Load Capacitance (max.) (Note 10-1) 27 pF
Series Resistance (max. ESR) 40