
ICS843021AG REVISION D OCTOBER 12, 2010
9
2010 Integrated Device Technology, Inc.
ICS843021 Data Sheet
FEMTOCLOCK CRYSTAL-TO-3.3V LVPECL CLOCK GENERATOR
Schematic Example
Figure 5A shows a schematic example of using an ICS843021. An
example of LVPECL termination is shown in this schematic.
Additional LVPECL termination approaches are shown in the
LVPECL Termination Application Note. In this example, an 18pF
parallel resonant crystal is used for generating 125MHz output
frequency. TheC1 = 27pF and C2 = 33pF are recommended for
frequency accuracy. For a different board layout, the C1 and C2
values may be slightly adjusted for optimizing frequency accuracy.
Figure 5. ICS843021 Schematic Example
Schematic Example
Figure 5B shows an example of ICS843021 P.C. board layout. The
crystal X1 footprint shown in this example allows installation of either
surface mount HC49S or through-hole HC49 package. The footprints
of other components in this example are listed in the Table 7 There
should be at least one decoupling capacitor per power pin. The
decoupling capacitors should be located as close as possible to the
power pins. The layout assumes that the board has clean analog
power ground plane.
Figure 5B. ICS843021 PC Board Layout Example
Table 7. Footprint Table
NOTE: Table 7 lists component sizes
shown in this layout example.
Reference
Size
C1, C2
0402
C3
0805
C4, C5
0603
R2
0603