Integrated
Circuit
Systems, Inc.
ICS84320-01
780MH
Z
, C
RYSTAL
-
TO
-3.3V D
IFFERENTIAL
LVPECL F
REQUENCY
S
YNTHESIZER
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. The ICS84320-01 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 bypass capacitors should be
used for each pin. To achieve optimum jitter performance,
power supply isolation is required.
Figure 2
illustrates how
a 24Ω resistor along with a 10µF and a .01µF bypass
capacitor should be connected to each V
CCA
pin.
3.3V
V
CC
.01µF
V
CCA
.01µF
10µF
24Ω
F
IGURE
2. P
OWER
S
UPPLY
F
ILTERING
C
RYSTAL
I
NPUT
I
NTERFACE
A crystal can be characterized for either series or parallel mode
operation. The ICS84320-01 has a built-in crystal oscillator circuit.
This interface can accept either a series or parallel crystal without
additional components and generate frequencies with accuracy
suitable for most applications. Additional accuracy can be
achieved by adding two small capacitors C1 and C2 as shown in
Figure 3.
25
C1
18p
X1
18pF Parallel Crystal
24
C2
22p
XTAL1
XTAL2
ICS84320-01
Figure 3. C
RYSTAL
I
NPU
t I
NTERFACE
84320AY-01
www.icst.com/products/hiperclocks.html
9
REV. A AUGUST 24, 2004
ICS [ INTEGRATED CIRCUIT SYSTEMS ]
