REVISION A 3/30/15
840002I DATA SHEET
9 FEMTOCLOCKS™ CRYSTAL-TOLVCMOS/
LVTTL FREQUENCY SYNTHESIZER
APPLICATION INFORMATION
As in any high speed analog circuitry, the power supply
pins are vulnerable to random noise. The 840002I pro-
vides separate power supplies to isolate any high switching
noise from the outputs to the internal PLL. V
DD
, V
DDA
, and
V
DDO
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
DDA
.
POWER SUPPLY FILTERING TECHNIQUES
FIGURE 1. POWER SUPPLY FILTERING
10Ω
V
DDA
10μF
.01μF
3.3V or 2.5V
.01μF
V
DD
CRYSTAL INPUT INTERFACE
The 840002I has been characterized with 18pF parallel resonant
crystals. The capacitor values shown in Figure 2 below were
Figure 2. CRYSTAL INPUt INTERFACE
determined using a 26.5625MHz 18pF parallel resonant crystal
and were chosen to minimize the ppm error.
840002I
40002
