Datasheet

Micrel, Inc.
KSZ8081MNX/KSZ8081RNB
August
19, 2015 65
Revision 1.4
Reference Clock – Connection and Selection
A crystal or external clock source, such as an oscillator, is used to provide the reference clock for the KSZ8081MNX/RNB.
For the KSZ8081MNX in all operating modes and for the KSZ8081RNB in RMII – 25MHz Clock Mode, the reference clock
is 25MHz. The reference clock connections to XI (Pin 9) and XO (Pin 8), and the reference clock selection criteria, are
provided in Figure 24 and Table 23.
Figure 24. 25MHz Crystal/Oscillator Reference Clock Connection
Table 23. 25MHz Crystal/Reference Clock Selection Criteria
Characteristics Value Units
Frequency 25 MHz
Frequency tolerance (max)
(15)
±50 ppm
Crystal series resistance (typ) 40 Ω
Crystal load capacitance (typ) 22 pF
Note:
15. ±60ppm for overtemperature crystal.
For the KSZ8081RNB in RMII – 50MHz clock mode, the reference clock is 50MHz. The reference clock connections to XI
(Pin 9), and the reference clock selection criteria are provided in Figure 25 and Table 24.
Figure 25. 50MHz Oscillator Reference Clock Connection
Table 24. 50MHz Oscillator/Reference Clock Selection Criteria
Characteristics Value Units
Frequency 50 MHz
Frequency tolerance (maximum) ±50 ppm