Datasheet
2016-2018 Microchip Technology Inc. DS00002202C-page 57
KSZ8081MNX/RNB
7.12 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 – 25
MHz Clock Mode, the refer-
ence clock is 25 MHz. The reference clock connections to XI (Pin 9) and XO (Pin 8), and the reference clock selection
criteria, are provided in Figure 7-14 and Table 7-11.
FIGURE 7-14: 25 MHZ CRYSTAL/OSCILLATOR REFERENCE CLOCK CONNECTION
Note 7-1 ±60 ppm for overtemperature crystal.
For the KSZ8081RNB in RMII – 50 MHz clock mode, the reference clock is 50 MHz. The reference clock connections
to XI (Pin 9), and the reference clock selection criteria are provided in Figure 7-15 and Table 7-12.
FIGURE 7-15: 50 MHZ OSCILLATOR REFERENCE CLOCK CONNECTION
TABLE 7-11: 25 MHZ CRYSTAL/REFERENCE CLOCK SELECTION CRITERIA
Characteristics Value Units
Frequency 25 MHz
Frequency tolerance (max) (Note 7-1) ±50 ppm
Crystal series resistance (typ) 40
Crystal load capacitance (typ) 22 pF
TABLE 7-12: 50 MHZ OSCILLATOR/REFERENCE CLOCK SELECTION CRITERIA
Characteristics Value Units
Frequency 50 MHz
Frequency tolerance (maximum) ±50 ppm
NC
XI
XO
25MHz OSC
±50PPM
XI
XO
25MHz XTAL
±50PPM
22pF
22pF
NC
XI
XO
50MHz OSC
±50PPM