Datasheet

 2017 Microchip Technology Inc. DS00002348A-page 89

KSZ8873MLL/FLL/RLL

9.0 SELECTION OF ISOLATION TRANSFORMERS

A 1:1 isolation transformer is required at the line interface. Use one with integrated common-mode chokes for designs

exceeding FCC requirements.

Table 9-1 lists recommended transformer characteristics.

TABLE 9-1: TRANSFORMER SELECTION CRITERIA

Parameter Value Test Conditions

Turns Ratio 1 CT : 1 CT —

Open-Circuit Inductance (min.) 350 µH 100 mV, 100 kHz, 8 mA

Leakage Inductance (max.) 0.4 µH 1 MHz (min.)

Interwinding Capacitance (max.) 12 pF —

D.C. Resistance (max.) 0.9 —

Insertion Loss (max.) –1.0 dB 0 MHz to 65 MHz

HIPOT (min.) 1500 V

RMS

—

TABLE 9-2: QUALIFIED SINGLE-PORT MAGNETICS

Manufacturer Part Number Auto MDI-X

Bel Fuse S558-5999-U7 Yes

Bel Fuse (MagJack) SI-46001 Yes

Bel Fuse (MagJack) SI-50170 Yes

Delta LF8505 Yes

LanKom LF-H41S Yes

Pulse H1102 Yes

Pulse (Low Cost) H1260 Yes

Datatronic NT79075 Yes

Transpower HB726 Yes

YCL LF-H41S Yes

TDK (MagJack) TLA-6T718 Yes

TABLE 9-3: TYPICAL REFERENCE CRYSTAL CHARACTERISTICS

Characteristic Value

Frequency 25.00000 MHz

Frequency Tolerance (max.) ±50 ppm

Load Capacitance (max.) 20 pF

Series Resistance 40