FEMTOCLOCKS
®
CRYSTAL-TO-
3.3V LVPECL CLOCK GENERATOR
843011 DATA SHEET
6 REVISION B 9/25/15
APPLICATION INFORMATION
Figure 2. CRYSTAL INPUt INTERFACE
CRYSTAL INPUT INTERFACE
The 843011 has been characterized with 18pF parallel
resonant crystals. The capacitor values, C1 and C2, shown in
Figure 2 below were determined using a 26.5625MHz, 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.
As in any high speed analog circuitry, the power supply
pins are vulnerable to random noise. The 843011 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 .01μF bypass
capacitor should be connected to each V
CCA
pin.
POWER SUPPLY FILTERING TECHNIQUES
FIGURE 1. POWER SUPPLY FILTERING
10Ω
V
CCA
10μF
.01μF
3.3V
.01μF
V
CC
