REVISION C 11/5/15
843081I-01 DATA SHEET
7 FEMTOCLOCKS
®
CRYSTAL-TO-
3.3V, 2.5V LVPECL CLOCK MULTIPLIER
APPLICATION INFORMATION
As in any high speed analog circuitry, the power supply
pins are vulnerable to random noise. The 843081I-01 pro-
vides 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 .01μF bypass
capacitor should be connected to each V
CCA
pin. The 10Ω resistor
can also be replaced by a ferrite bead.
POWER SUPPLY FILTERING TECHNIQUES
FIGURE 1. POWER SUPPLY FILTERING
10Ω
V
CCA
10μF
.01μF
3.3V or 2.5V
.01μF
V
CC
Figure 2. CRYSTAL INPUt INTERFACE
CRYSTAL INPUT INTERFACE
The 843081I-01 has been characterized with 18pF parallel
resonant crystals. The capacitor values, C1 and C2, shown in
Figure 2 below were determined using an 18pF parallel reso-
nant crystal and were chosen to minimize the ppm error. The
optimum C1 and C2 values can be slightly adjusted for different
board layouts.
ICS843081I-01
