3.0 Functional Description (Continued)
X2
20 MHz
OSC
X1
20 MHz TO 10 Mb/s SECTION
50ppm
OSCIN
CLK25M
REFIN
TX_CLK
DIV 2.0
4.7 kΩ
25 MHz TO 100 Mb/s SECTION
25 MHz SYSTEM
REFERENCE
50ppm
25 MHz FROM 100 Mb/s SECTION
2.5 MHz (OR 10 MHz) FROM 10 Mb/s SECTION
MUX
SPEED
SELECT
FIGURE 9. 25 MHz and 20 MHz References
X2
VCC
4.7 kΩ
X1
TO 10 Mb/s SECTION
DIV 2.5
OSCIN
DIV 2.0
CLK25M
REFIN
25 MHz TO 100 Mb/s SECTION
25 MHz SYSTEM
REFERENCE
50ppm
TX_CLK
25 MHz FROM 100 Mb/s SECTION
MUX
FROM 10 Mb/s SECTION
SPEED
SELECT
FIGURE 10. Single 25 MHz Reference
Version A
National Semiconductor
26