
ICS843001AGI-22 REVISION B JUNE 25, 2009
15
2009 Integrated Device Technology, Inc.
ICS843001I-22 Data Sheet
FEMTOCLOCK CRYSTAL/LVCMOS-TO-3.3V, 2.5V LVPECL FREQUENCY SYNTHESIZER
Schematic Layout
Figure 6 shows an example of ICS843001I-22 application
schematic. In this example, the device is operated at VCC =
VCCO_LVCMOS = VCCO_LVPECL = 3.3V. The 18pF parallel resonant
25MHz crystal is used. The C1 = C2 = 22pF and C4 = C5 = 22pF
are recommended for frequency accuracy. For different board
layouts, the C1, C2, C4 and C5 may be slightly adjusted for
optimizing frequency accuracy. Two examples of LVPECL
terminations and one example of LVCMOS are shown in this
schematic. Additional termination approaches are shown in the
LVPECL Termination Application Note.
ICS843001I-22 Layout Example
VCC
Zo = 50 Ohm
C9
.1uf
MR
Q
C4
22pF
C6
10u
M1
Q
Zo = 50 Ohm
RU3
1K
XTAL_IN0
M0
VCC=3.3V
C5
22pF
VCC
R10
50
M2
R2
133
VCCO
VCCA
/Q
Q
RD2
1K
3.3V
SEL1
VCCO_LVCMOS=3.3V
C3
.1uf
R8
50
+
-
(U1:1)
Zo = 50 Ohm
C1
22pF
C8
.1uf
R9
43
R5
82.5
R6
82.5
Ro ~ 7 Ohm
Q1
Driv er_LVCMOS
N1
LVCMOS
1 8 p F
RU1
1K
OE
C7
0.1u
Zo = 50 Ohm
Logic Control Input Examples
U1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
VCCO_LVCMOS
N0
N1
N2
VCCO_LVPECL
Q
nQ
VEE
VCCA
VCC
XTAL_OUT1
XTAL_IN1
XTAL_OUT0
XTAL_IN0
CLK
SEL0
SEL1
MR
M0
M1
M2
OE
VEE
REF_OUT
R4
10
X2
26.5625MHz
R1
33
nQ
X1
25MHz
VCCO_LVCMOS
N0
C2
22pF
VCCO_LVPECL=3.3V
VDDO
N2
CLK
SEL0
RD3
1K
R7
50
VCCO_LVPECL
/Q
(U1:5)
VCC
TL3
Zo = 50 Ohm
1 8 p F
Optional
LVPECL
Y-Termination
RD1
Not Install
To Logic
Input
pins
REF_OUT
TL2
Zo = 50 Ohm
Set Logic
Input to
'1'
R3
133
VCC
XTAL_OUT1
XTAL_OUT0
Set Logic
Input to
'0'
RU2
Not Install
To Logic
Input
pins
VCC
VDD
XTAL_IN1
+
-