ICS84327AMT View Datasheet(PDF) - Integrated Circuit Systems
Part Name
Description
MFG CO.
ICS84327AMT
Integrated Circuit Systems
'ICS84327AMT' PDF : 15 Pages View PDF
Integrated
Circuit
Systems, Inc.
PRELIMINARY
ICS84327
CRYSTAL-TO-3.3V LVPECL
FREQUENCY SYNTHESIZER W/INTEGRATED FANOUT BUFFER
CRYSTAL INPUT INTERFACE
The ICS84327 has been characterized with 18pF parallel reso-
nant crystals. The capacitor values shown in Figure 4 below were
determined using a 25MHz 18pF parallel resonant crystal and
were chosen to minimize the ppm error.
25MHz X1
19
C1
18pF
XTAL2
20
C2
22pF
XTAL1
ICS84327
Figure 4. CRYSTAL INPUt INTERFACE
SCHEMATIC EXAMPLE
Figure 5A shows a schematic example of using an ICS84327.
In this example, the input is a 25MHz parallel resonant crystal
with load capacitor CL=18pF. The frequency fine tuning
capacitors C1 and C2 is 22pF and 18pF respectively. This
example also shows logic control input handling. The configu-
ration is set at F_SEL[2:0]=011, therefore, the output frequency
is 625MHz. It is recommended to have one decouple capaci-
tor per power pin. Each decoupling capacitor should be lo-
cated as close as possible to the power pin. The low pass
filter R7, C11 and C16 for clean analog supply should also be
located as close to the VCCA pin as possible.
VCC
VCC
R7
24
C 11
0.1u
C16
10u
VCC
VCCA
22p
C1
X1
25MHz,18pF
C2
18p
R4 VCC
1K
F_SEL2
F_SEL1
R5 F_SEL0
1K
U1
13
14
15
VC C O
VEE
16 PLL_SEL
17 VCC
18
19
20
21
VC C A
F_SEL2
XTAL2
XTAL1
22
23
24
MR
F_SEL1
F_SEL0
VC C O
I C S84327
nQ5
Q5
12
11
10
nQ4 9
Q4
nQ3
Q3
nQ2
Q2
nQ1
Q1
nQ0
Q0
8
7
6
5
4
3
2
1
Zo = 50
Zo = 50
R2
50
RU1
SP
RU2
1K
RU3
1K
F_SEL2
F_SEL1
F_SEL0
VCC=3.3V
(U1,13) VCC
(U 1, 16)
(U1,24)
RD1
1K
RD2
SP
RD3
SP
e.g. F_SEL[2:0]=011
SP = Spare, Not Installed
C6
0.1u
C5
0.1u
C3
0.1u
-
+
R1
50
R3
50
84327AM
FIGURE 5A. ICS84327 SCHEMATIC EXAMPLE
www.icst.com/products/hiperclocks.html
9
REV. A SEPTEMBER 18, 2003
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