ICS84326AM Ver la hoja de datos (PDF) - Integrated Circuit Systems
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Fabricante
ICS84326AM
Integrated Circuit Systems
ICS84326AM Datasheet PDF : 15 Pages
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Integrated
Circuit
Systems, Inc.
PRELIMINARY
ICS84326
CRYSTAL-TO-3.3V LVPECL
SERIAL ATTACHED SCSI CLOCK SYNTHESIZER/FANOUT BUFFER
CRYSTAL INPUT INTERFACE
The ICS84326 has been characterized with 18pF parallel
resonant crystals. The capacitor values, C1 and C2, shown
in Figure 4 below were determined using a 25MHz, 18pF
parallel resonant crystal and were chosen to minimize the
ppm error. The optimum C1 and C2 values can be slightly
adjusted for different board layouts.
25MHz X1
19
C1
18pF
XTAL2
20
C2
22pF
XTAL1
ICS84326
Figure 4. CRYSTAL INPUt INTERFACE
SCHEMATIC EXAMPLE
Figure 5A shows a schematic example of using an ICS84326. 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 configuration is set at F_SEL=0,
therefore, the output frequency is 150MHz. It is recommended to
have one decouple capacitor per power pin. Each decoupling ca-
pacitor should be located 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 V pin as possible.
CCA
VCC
R7
24
C11
0.1u
C 16
10u
VCC
VCCA
22p
C1
X1
25MHz,18pF
C2
18p
R4 VCC
1K
R5
1K
R6
1K
U1
13
14
15
VCCO
VEE
16
17
18
19
20
PLL_SEL
VCC
VCCA
nc
XTAL2
21
22
XTAL1
MR
23 nc
24
F_SEL
VCCO
ICS84326
12
nQ5
Q5
11
10
nQ4
Q4
nQ3
Q3
nQ2
9
8
7
6
5
Q2
nQ1
4
3
Q1 2
nQ0
Q0
1
Zo = 50
Zo = 50
R2
50
-
+
R1
50
R3
50
VCC=3.3V
(U1,13) VCC
C6
0.1u
(U 1,16)
(U1,24)
C5
0.1u
C3
0.1u
84326AM
FIGURE 5A. ICS84326 SCHEMATIC EXAMPLE
www.icst.com/products/hiperclocks.html
9
REV. A MARCH 10, 2003
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