Datasheet KSZ8999 (Microchip) - 51

Micrel, Inc. KS8999 Selection of Isolation Transformer(1)
One simple 1:1 isolation transformer is needed at the line interface. An isolation transformer with integrated commonmode choke is recommended for exceeding FCC requirements. The following table gives recommended transformer
characteristics.
Characteristics Name Value Turns Ratio Test Condition 1 CT : 1 CT Open-Circuit Inductance (min.) 350µH 100mV, 100 KHz, 8mA Leakage Inductance (max.) 0.4µH 1MHz (min.) Inter-Winding Capacitance (max.) 12pF D.C. Resistance (max.) 0.9Ω Insertion Loss (max.) 1.0dB HIPOT (min.) 0MHz to 65MHz 1500Vrms Note:
1. The IEEE 802.3u standard for 100BaseTX 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. Selection of Reference Oscillator/Crystal
An oscillator or crystal with the following typical characteristics is recommended.
Characteristics Name Value Test Condition 25.00000 MHz Maximum Frequency Tolerance ±50 ppm Maximum Jitter 150 ps(pk-pk) Frequency The following transformer vendors provide compatible magnetic parts for Micrel’s device:
4-Port Integrated Single Port Vendor Part Auto
MDIX Number
of Ports Vendor Part Auto
MDIX Number
of Ports Pulse H1164 Yes 4 Pulse H1102 Yes 1 Bel Fuse 558-5999-Q9 Yes 4 Bel Fuse S558-5999-U7 Yes 1 YCL PH406466 Yes 4 YCL PT163020 Yes 1 Transpower HB826-2 Yes 4 Transpower HB726 Yes 1 Delta LF8731 Yes 4 Delta LF8505 Yes 1 Table 15. Qualified Magnetics Vendor Lists January 2005 51 KS8999