ICS843301I-108 Datasheet, PDF (6/15 Pages) Integrated Device Technology – FEMTOCLOCKS™ CRYSTAL-TO-3.3V, 2.5V LVPECL 75MHZ FREQUENCY SYNTHESIZER W/SSC

ICS843301I-108
FEMTOCLOCKS™ CRYSTAL-TO-3.3V, 2.5V LVPECL FREQUENCY SYNTHESIZER W/SSC
APPLICATION INFORMATION
PRELIMINARY
POWER SUPPLY FILTERING TECHNIQUES
As in any high speed analog circuitry, the power supply pins
are vulnerable to random noise. The ICS843301I-108 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 1 illustrates how a 10Ω resistor along with a
10μF and a 0.01μF bypass capacitor should be connected to
each V_CCA pin.
3.3V or 2.5V
V_CC
.01μF 10Ω
V
CCA
.01μF
10μF
FIGURE 1. POWER SUPPLY FILTERING
CRYSTAL INPUT INTERFACE
The ICS843301I-108 has been characterized with 18pF parallel
resonant crystals. The capacitor values, C1 and C2, shown in
Figure 2 below were determined using a 20MHz, 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
Crystal
XTAL_IN
C1
XTAL_OUT
C2
FIGURE 2. CRYSTAL INPUt INTERFACE
IDT^™ / ICS^™ 3.3V, 2.5V LVPECL FREQUENCY SYNTHESIZER W/SSC 6
ICS843301BGI-108 REV. A OCTOBER 9, 2007