ICS843207-350
FEMTOCLOCKS™ CRYSTAL-TO-LVPECL 350MHZ FREQUENCY MARGINING SYNTHESIZER
PRELIMINARY
A
PPLICATION
I
NFORMATION
P
OWER
S
UPPLY
F
ILTERING
T
ECHNIQUES
As in any high speed analog circuitry, the power supply pins are
vulnerable to random noise. To achieve optimum jitter perfor-
mance, power supply isolation is required. The ICS843207-350
provides separate power supplies to isolate any high switching
noise from the outputs to the internal PLL. V
CC
, V
CCA
and V
CCO
should be individually connected to the power supply plane
through vias, and 0.01µF bypass capacitors should be used
for each pin.
Figure 1
illustrates this for a generic V
CC
pin and
also shows that V
CCA
requires that an additional 10Ω resistor
along with a 10µF bypass capacitor be connected to the V
CCA
pin.
3.3V
V
CC
.01μF
V
CCA
.01μF
10μF
10Ω
F
IGURE
1. P
OWER
S
UPPLY
F
ILTERING
C
RYSTAL
I
NPUT
I
NTERFACE
The ICS843207-350 has been characterized with 18pF
parallel resonant crystals. The capacitor values shown in
Figure 2
below were determined using a 14MHz, 18pF parallel
resonant crystal and were chosen to minimize the ppm error.
XTAL_OUT
C1
27p
X1
18pF Parallel Crystal
XTAL_IN
C2
27p
F
IGURE
2. C
RYSTAL
I
NPU
t I
NTERFACE
IDT
™
/ ICS
™
LVPECL FREQUENCY MARGINING SYNTHESIZER
8
ICS843207CY-350 REV. A DECEMBER 3, 2007
IDT [ INTEGRATED DEVICE TECHNOLOGY ]
