ICS843003 Datasheet, PDF (10/17 Pages) Integrated Circuit Systems – FEMTOCLOCKS CRYSTAL-TO-3.3V LVPECL FREQUENCY SYNTHESIZER

Integrated
Circuit
Systems, Inc.
ICS843003
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 ICS843003 provides sepa-
rate 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.
V
CC
V
CCA
3.3V
.01µF 10 Ω
.01µF
10µF
FIGURE 2. POWER SUPPLY FILTERING
CRYSTAL INPUT INTERFACE
The ICS843003 has been characterized with 18pF parallel
resonant crystals. The capacitor values shown in Figure 3
below were determined using a 31.25MHz or 26.041666MHz
18pF parallel resonant crystal and were chosen to minimize
the ppm error.
X1
18pF Parallel Crystal
XTAL_OUT
C1
33p
XTAL_IN
C2
27p
ICS843003
Figure 3. CRYSTAL INPUt INTERFACE
843003AG
www.icst.com/products/hiperclocks.html
10
REV. A JULY 27, 2004