ICS8430-61 Datasheet, PDF (9/15 Pages) Integrated Circuit Systems – 500MHZ, CRYSTAL-TO-3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER

Integrated
Circuit
Systems, Inc.
ICS8430-61
500MHZ, CRYSTAL-TO-3.3V DIFFERENTIAL
LVPECL FREQUENCY SYNTHESIZER
CRYSTAL INPUT INTERFACE
The ICS8430-61 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 par-
allel resonant crystal and were chosen to minimize the ppm
error. These same capacitor values will tune any 18pF paral-
lel resonant crystal over the frequency range and other pa-
rameters specified in this data sheet. The optimum C1 and C2
values can be slightly adjusted for different board layouts.
X1
18pF Parallel Cry stal
XTAL_IN
C1
22p
XTAL_OUT
C2
22p
IC_ICS_S8₈4₄3₃32_0-61
Figure 4. CRYSTAL INPUt INTERFACE
LAYOUT GUIDELINE
The schematic of the ICS8430-61 layout example used in this
layout guideline is shown in Figure 5A. The ICS8430-61 rec-
ommended PCB board layout for this example is shown in
Figure 5B. This layout example is used as a general guideline.
The layout in the actual system will depend on the selected
component types, the density of the components, the density
of the traces, and the stack up of the P.C. board.
8430AY-61
U1
1
2
M5
3
4
5
6
M6
M7
M8
N0
7
8
N1
N2
VEE
C1
C2
X1
VCC
XTAL_IN
REF_IN
nXTAL_SEL
24
23
22
21
R EF _I N
XTAL_SEL
VCCA
S_LOAD
S_DATA
S_CLOCK
MR
20
19
18
17
S_LOAD
S_DATA
S_CLOCK
VCCA
C11
0. 01u
R7
10
C16
10u
8430-61
C14
0.1u
C15
0.1u
Zo = 50 Ohm
IN+
TL1
Zo = 50 Ohm
IN-
TL2
VCC
R1
R3
125
125
+
-
R2
R4
84
84
FIGURE 5A. SCHEMATIC OF RECOMMENDED LAYOUT
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9
REV. A JULY 22, 2004