参数资料
型号: 021AL
英文描述: FEMTOCLOCKS-TM CRYSTAL-TO- 3.3V LVPECL CLOCK GENERATOR
中文描述: FEMTOCLOCKS -商标晶体至3.3V的LVPECL时钟发生器
文件页数: 11/13页
文件大小: 189K
代理商: 021AL
843021AG
www.icst.com/products/hiperclocks.html
REV. C MARCH 31, 2005
7
Integrated
Circuit
Systems, Inc.
ICS843021
FEMTOCLOCKSCRYSTAL-TO-
3.3V LVPECL CLOCK GENERATOR
APPLICATION SCHEMATIC
Figure 3A shows a schematic example of the ICS843021. An
example of LVEPCL termination is shown in this schematic.
Additional LVPECL termination approaches are shown in the
LVPECL Termination Application Note. In this example, an 18pF
parallel resonant 25MHz crystal is used for generating 125MHz
output frequency. The C1 = 27pF and C2 = 33pF are recom-
mended for frequency accuracy. For different board layout, the
C1 and C2 values may be slightly adjusted for optimizing fre-
quency accuracy.
FIGURE 3A. ICS843021 SCHEMATIC EXAMPLE
FIGURE 3B. ICS843021 PC BOARD LAYOUT EXAMPLE
PC BOARD LAYOUT EXAMPLE
Figure 3B shows an example of ICS843021 P.C. board layout.
The crystal X1 footprint shown in this example allows installa-
tion of either surface mount HC49S or through-hole HC49 pack-
age.The footprints of other components in this example are listed
in the
Table 6. There should be at least one decoupling capacitor
per power pin. The decoupling capacitors should be located as
close as possible to the power pins. The layout assumes that
the board has clean analog power ground plane.
TABLE 6. FOOTPRINT TABLE
e
c
n
e
r
e
f
e
Re
z
i
S
2
C
,
1
C2
0
4
0
3
C5
0
8
0
5
C
,
4
C3
0
6
0
2
R3
0
6
0
t
n
e
n
o
p
m
o
c
s
t
s
il
,
6
e
l
b
a
T
:
E
T
O
N
.
e
l
p
m
a
x
e
t
u
o
y
a
l
s
i
h
t
n
i
n
w
o
h
s
e
z
i
s
Zo = 50 Ohm
VCC
X1
25MHz
VCC=3.3V
C3
10uF
VCC
C1
27pF
Q
C5
0.1u
R3
133
C2
33pF
VCC
Zo = 50 Ohm
U1
ICS843011
1
2
3
4
8
7
6
5
VCCA
VEE
XTAL_OUT
XTAL_IN
VCC
Q0
nQ0
NC
R4
82.5
C4
0.01u
R5
133
nQ
VCCA
R6
82.5
18pF
R2
10
+
-
ICS843021
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