![](http://datasheet.mmic.net.cn/100000/ICS8431CM-01LF_datasheet_3492612/ICS8431CM-01LF_8.png)
8431CM-01
www.icst.com/products/hiperclocks.html
REV. B FEBRUARY 3, 2003
8
Integrated
Circuit
Systems, Inc.
ICS8431-01
200MHZ, LOW JITTER,
CRYSTAL OSCILLATOR-TO-3.3V LVPECL FREQUENCY SYNTHESIZER
The clock layout topology shown below is typical for
IA64/32 platforms. The two different layouts mentioned are
recommended only as guidelines.
FOUT and nFOUT are low impedance follower outputs that
generate ECL/LVPECL compatible outputs. Therefore, terminat-
ing resistors (DC current path to ground) or current sources
must be used for functionality. These outputs are designed to
FIGURE 4B. LVPECL OUTPUT TERMINATION
3.3V
FOUT
FIN
5
2 Zo
Z
o
5
2
Z
o
3
2
Z
o
3
2
Z
o = 50
Z
o = 50
FIGURE 4A. LVPECL OUTPUT TERMINATION
RTT =
1
(V
OH + VOL / VCC –2) –2
Z
o
Z
o = 50
Z
o = 50
50
50
RTT
VCC-2V
FIN
FOUT
FIGURE 5A. RECOMMENDED SCHEMATIC LAYOUT
drive 50
transmission lines. Matched impedance techniques
should be used to maximize operating frequency and minimize
signal distortion.
Figures 4A and 4B show two different layouts
which are recommended only as guidelines. Other suitable clock
layouts may exist and it would be recommended that the board
designers simulate to guarantee compatibility across all printed
circuit and clock component process variations.
R1
125
VCC
IN-
VCC
U1
8431-01
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
28
27
26
25
nc
SSC_CTL0
SSC_CTL1
VEE
TEST_IO
VCC
VEE
nFOUT
FOUT
VCCO
nc
VEE
VCCA
nc
VCCI
XTAL2
XTAL1
R3
125
R2
84
VCC0
C2
0.1uF
TL1
Zo = 50 Ohm
Termination A
VCC
VCCA
R1
50
IN-
X1
IN+
R4
84
C1
0.1uF
IN+
C3
0.01uF
R5
10
R3
50
TL2
Zo = 50 Ohm
Termination
B (not shown
in the layout)
R2
50
C4
10uF
C5
0.01uF
LAYOUT GUIDELINE
The schematic of the ICS8431-01 layout example used in
this layout guideline is shown in
Figure 5A. The ICS8431-01
recommended PCB board layout for this example is shown
in
Figure 5B. This layout example is used as a general guide-
line. 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.
TERMINATION FOR LVPECL OUTPUTS