ICS843204I Datasheet, PDF (6/12 Pages) Integrated Circuit Systems – FEMTOCLOCKS™ CRYSTAL-TO-3.3V LVPECL FREQUENCY SYNTHESIZER

Integrated
Circuit
Systems, Inc.
PRELIMINARY
ICS843204I
FEMTOCLOCKS™ CRYSTAL-TO-
3.3V LVPECL FREQUENCY SYNTHESIZER
APPLICATION INFORMATION
POWER SUPPLY FILTERING TECHNIQUES
As in any high speed analog circuitry, the power supply pins
are vulnerable to random noise. The ICS843204I provides
separate power supplies to isolate any high switching
noise from the outputs to the internal PLL. V_CC, V_CCA, and
V_{CCO_x} should be individually connected to the power sup-
ply plane through vias, and bypass capacitors should be
used for each pin. To achieve optimum jitter performance,
power supply isolation is required. Figure 1 illustrates how
a 10Ω resistor along with a 10µF and a .01μF bypass
capacitor should be connected to each V_CCA.
3.3V
V
CC
.01μF 10Ω
V_CCA
.01μF
10μF
FIGURE 1. POWER SUPPLY FILTERING
CRYSTAL INPUT INTERFACE
The ICS843204I has been characterized with 18pF
parallel resonant crystals. The capacitor values shown in
Figure 2 below were determined using an 18pF parallel
resonant crystal and were chosen to minimize the ppm error.
X1
18pF Parallel Crystal
XTAL_OUT
C1
33p
XTAL_IN
C2
27p
ICS843204I
Figure 2. CRYSTAL INPUt INTERFACE
843204AGI
www.icst.com/products/hiperclocks.html
6
REV. A JANUARY 6, 2006