Datasheet

Micrel, Inc. KS8999
January 2005
51
KS8999
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. The following table gives recommended transformer
characteristics.
Characteristics Name Value Test Condition
Turns Ratio 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 0MHz to 65MHz
HIPOT (min.) 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
Frequency 25.00000 MHz
Maximum Frequency Tolerance ±50 ppm
Maximum Jitter 150 ps(pk-pk)
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