3.0 Functional Description (Continued)
X2
50ppm
20 MHz
OSC
X1
20 MHz TO 10 Mb/s SECTION
50 MHz
OSC
OSCIN
CLK25M
REFIN
TX_CLK
DIV 2.0
50ppm
25 MHz TO 100 Mb/s SECTION
25 MHz FROM 100 Mb/s SECTION
2.5 MHz (OR 10 MHz) FROM 10 Mb/s SECTION
MUX
SPEED
SELECT
FIGURE 7. 50 MHz and 20 MHz References
* 33 pF
* 33 pF
X2
X1
20 MHZ
0.005%
20 MHz TO 10 Mb/s SECTION
OSCIN
CLK25M
REFIN
DIV 2.0
50 MHz
OSC
50ppm
25 MHz TO 100 Mb/s SECTION
TX_CLK
25 MHz FROM 100 Mb/s SECTION
2.5 MHz (OR 10 MHz) FROM 10 Mb/s SECTION
MUX
SPEED
SELECT
* NOTE: REFER TO CRYSTAL MANUFACTURE FOR RECOMMENDED CRYSTAL LOAD CAPACITANCE
FIGURE 8. 50 MHz Reference and 20 MHz Crystal
Version A
National Semiconductor
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