ICS843004 Datasheet, PDF (10/16 Pages) Integrated Circuit Systems – FEMTOCLOCKS™ LVCMOS/CRYSTAL-TO- 3.3V LVPECL FREQUENCY SYNTHESIZER

Integrated
Circuit
Systems, Inc.
ICS843004
FEMTOCLOCKS™ LVCMOS/CRYSTAL-TO-
3.3V LVPECL FREQUENCY SYNTHESIZER
CRYSTAL INPUT INTERFACE
The ICS843004 has been characterized with 18pF parallel
resonant crystals. The capacitor values shown in Figure 3
below were determined using a 26.5625MHz 18pF parallel
resonant crystal and were chosen to minimize the ppm error.
X1
18pF Parallel Crystal
XTAL_OUT
C1
33p
XTAL_IN
C2
27p
ICS843004
Figure 3. CRYSTAL INPUt INTERFACE
LAYOUT GUIDELINE
Figure 4 shows a schematic example of the ICS843004. An ex-
ample of LVEPCL termination is shown in this schematic. Addi-
tional LVPECL termination approaches are shown in the LVPECL
Termination Application Note. In this example, an 18pF parallel
resonant 26.5625MHz crystal is used. The C1=27pF and
C2=33pF are recommended for frequency accuracy. For differ-
ent board layout, the C1 and C2 may be slightly adjusted for
optimizing frequency accuracy.
VCC
R2
10 C3
10uF
Logic Control Input Examples
Set Logic
VDD _{Input to}
'1'
RU1
1K
To Logic
Input
pins
RD1
Not Install
Set Logic
VDD _{Input to}
'0'
RU2
Not Install
To Logic
Input
pins
RD2
1K
VCCA
C4
0.01u
VCC
C6
0.1u
U1
I C S843004
C2
33pF
X1
25MHz
18pF
C1
27pF
C9
0.1u
3. 3V
R3
133
Zo = 50 Ohm
VCCO
C7
0. 1u
Zo = 50 Ohm
R4
82. 5
R5
133
+
-
R6
82.5
VCC=3.3V
VCCO=3.3V
R7
133
Zo = 50 Ohm
3.3V
C8
0.1u
Zo = 50 Ohm
R8
82. 5
R9
133
+
-
R10
82.5
843004AG
FIGURE 4. ICS843004 SCHEMATIC EXAMPLE
www.icst.com/products/hiperclocks.html
10
REV. A NOVEMBER 18, 2004