Micrel, Inc.
KSZ9021RL/RN
Reference Clock – Connection and Selection
A crystal or external clock source, such as an oscillator, is used to provide the reference clock for the KSZ9021RL/RN.
The reference clock is 25 MHz for all operating modes of the KSZ9021RL/RN.
The following figure and table shows the reference clock connection to pins XI and XO of the KSZ9021RL/RN, and the
reference clock selection criteria.
22pF
22pF
XI
XI
25MHz OSC
+/-50ppm
22pF
22pF
NC
XO
XO
NC
25MHz XTAL
+/-50ppm
Figure 12. 25MHz Crystal / Oscillator Reference Clock Connection
Characteristics
Value
25
Units
MHz
ppm
Frequency
Frequency tolerance (max)
±50
Table 14. Reference Crystal/Clock Selection Criteria
Magnetics Specification
A 1:1 isolation transformer is required at the line interface. An isolation transformer with integrated common-mode chokes
is recommended for exceeding FCC requirements.
The following tables provide recommended magnetic characteristics and a list of qualified magnetics for the
KSZ9021RL/RN.
Parameter
Value
Test Condition
Turns ratio
1 CT : 1 CT
350µH
Open-circuit inductance (min.)
Insertion loss (max.)
HIPOT (min.)
100mV, 100kHz, 8mA
0MHz – 100MHz
1.0dB
1500Vrms
Table 15. Magnetics Selection Criteria
Magnetic Manufacturer
Part Number
H5007NL
Auto MDI-X
Yes
Number of Port
Pulse
TDK
1
1
TLA-7T101LF
Yes
Table 16. Qualified Single Port 10/100/1000 Magnetics
M9999-101309-1.1
October 2009
53
MICREL [ MICREL SEMICONDUCTOR ]
