ICS84329B Datasheet, PDF (8/19 Pages) Integrated Circuit Systems – 700MHZ, LOW JITTER, CRYSTAL-TO-3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER

Integrated
Circuit
Systems, Inc.
ICS84329B
700MHZ, LOW JITTER, CRYSTAL-TO-3.3V
DIFFERENTIAL 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 ICS84329B provides
separate power supplies to isolate any high switching
noise from the outputs to the internal PLL. V_CC and V_CCA
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. The 10Ω
resistor can also be replaced by a ferrite bead.
V
CC
V_CCA
3.3V
.01μF 10Ω
.01μF 10μF
FIGURE 2. POWER SUPPLY FILTERING
CRYSTAL INPUT INTERFACE
The ICS84329B has been characterized with 18pF parallel
resonant crystals. The capacitor values, C1 and C2, shown
in Figure 3 below were determined using a 25MHz, 18pF
parallel resonant crystal and were chosen to minimize the
ppm error. The optimum C1 and C2 values can be slightly
adjusted for different board layouts.
X1
18pF Parallel Cry stal
XTAL_IN
C1
22p
XTAL_OUT
C2
22p
ICS84332
Figure 3. CRYSTAL INPUt INTERFACE
RECOMMENDATIONS FOR UNUSED INPUT PINS
INPUTS:
LVCMOS CONTROL PINS:
All control pins have internal pull-ups or pull-downs; additional
resistance is not required but can be added for additional
protection. A 1kΩ resistor can be used.
84329BV
www.icst.com/products/hiperclocks.html
8
REV. B JANUARY 18, 2006