ICS8442 Datasheet, PDF (9/15 Pages) Integrated Circuit Systems – 700MHZ, CRYSTAL OSCILLATOR-TO-DIFFERENTIAL LVDS FREQUENCY SYNTHESIZER

Integrated
Circuit
Systems, Inc.
ICS8442
700MHZ, CRYSTAL OSCILLATOR-TO-DIFFERENTIAL
LVDS FREQUENCY SYNTHESIZER
CRYSTAL INPUT INTERFACE
A crystal can be characterized for either series or parallel mode
operation. The ICS8442 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. Typical results using parallel 18pF crystals are shown
in Table 10.
X1
18pF Parallel Crystal
25
C1
18p
XTAL2
24
C2
22p
XTAL1
ICS8442
Figure 3. CRYSTAL INPUt INTERFACE
LVDS DRIVER TERMINATION
A general LVDS interface is shown in Figure 4. In a 100Ω differ-
ential transmission line environment, LVDS drivers require a
matched load termination of 100Ω across near the receiver in-
put. For a multiple LVDS outputs buffer, if only partial outputs
are used, it is recommended to terminate the un-used outputs.
3.3V
Zo = 50 Ohm
3.3V
LVDS_DRIVER
R1
100
Zo = 50 Ohm
CLK
nCLK
HiPerClockS
100Ω Differential Transmission Line
FIGURE 4. TYPICAL LVDS DRIVER TERMINATION
8442AY
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9
REV. C JULY 8, 2004