3. TECHNICAL BRIEF
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3. TECHNICAL BRIEF
3.1.4 20 MHz Clock (Crystal, X400)
For the generation of the reference frequency for BCM5358U an external Crystal unit is used.
The XTAL ground is separated from main ground for reducing noise. It is used for the various clocks,
including the clock for the 10/100 MAC core (25 MHz) and the MIPS32 74K, UART, and USB 2.0 host in
BCM5358U.
Figure 3.4 Crystal Circuit diagram
600
FB400
220
R407
0
R406
33p
C422
33p
C423
20MHz
CXC3X200000GHVRG00
EXXY0027801
X400
4
2
3
1
HOT1
HOT2
GND1
GND2
600
FB401
XTAL_OUT
XTAL_IN
XTAL_GND
GND
20MHz CRYSTAL