ICS8430252-45 Datasheet, PDF (7/13 Pages) Integrated Circuit Systems – FEMTOCLOCKS™ CRYSTAL-TO-3.3V LVPECL FREQUENCY SYNTHESIZER

Integrated
Circuit
Systems, Inc.
PRELIMINARY
ICS8430252-45
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 ICS8430252-45 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 supply
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 pin.
V
CC
V
CCA
3.3V
.01μF 10 Ω
.01μF
10μF
FIGURE 1. POWER SUPPLY FILTERING
CRYSTAL INPUT INTERFACE
The ICS8430252-45 has been characterized with 18pF
parallel resonant crystals. The capacitor values shown in
Figure 2 below were determined using a 25MHz, 18pF
parallel resonant crystal and were chosen to minimize the
ppm error.
X1
18pF Parallel Crystal
XTAL_OUT
C1
22p
XTAL_IN
C2
22p
Figure 2. CRYSTAL INPUt INTERFACE
8430252CG-45
www.icst.com/products/hiperclocks.html
7
REV. B DECEMBER 9, 2005