FemtoClock
®
Crystal-to-3.3V LVPECL Frequency Synthesizer
843003I-01 DATA SHEET
9 REVISION A 12/8/14
APPLICATION INFORMATION
CRYSTAL INPUT INTERFACE
The ICS843003I-01 has been characterized with 18pF
parallel resonant crystals. The capacitor values shown in
Figure 3 below were determined using a 19.53125MHz or 25MHz,
Figure 3. CRYSTAL INPUt INTERFACE
18pF parallel resonant crystal and were chosen to minimize the
ppm error.
POWER SUPPLY FILTERING TECHNIQUES
As in any high speed analog circuitry, the power supply pins
are vulnerable to random noise. The ICS843003I-01 pro-
vides separate power supplies to isolate any high switching
noise from the outputs to the internal PLL. V
CC
, V
CCA
, and
V
CCOx
should be individually connected to the power supply
plane through vias, and bypass capacitors should be
used for each pin. To achieve optimum jitter performance,
power supply isolation is required. Figure 2 illustrates how
a 10Ω resistor along with a 10μF and a .01μF bypass
capacitor should be connected to each V
CCA
pin.
FIGURE 2. POWER SUPPLY FILTERING
10Ω
V
CCA
10μF
.01μF
3.3V
.01μF
V
CC
