ICS84329B datasheet(8/19 Pages) ICST

8 / 19 page

84329BV

www.icst.com/products/hiperclocks.html

REV. B JANUARY 18, 2006

Integrated

Circuit

Systems, Inc.

ICS84329B

700MHZ, LOW JITTER, CRYSTAL-TO-3.3V

DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER

APPLICATION INFORMATION

As in any high speed analog circuitry, the power supply pins

are vulnerable to random noise. The ICS84329B provides

separate power supplies to isolate any high switching

noise from the outputs to the internal PLL. V

CC and VCCA

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 10

Ω resistor along with a 10μF and a .01μF bypass

capacitor should be connected to each V

CCA pin. The 10Ω

resistor can also be replaced by a ferrite bead.

FIGURE 2. POWER SUPPLY FILTERING

CCA

μF

.01

μF

3.3V

.01

μF

POWER SUPPLY FILTERING TECHNIQUES

CRYSTAL INPUT INTERFACE

The ICS84329B has been characterized with 18pF parallel

resonant crystals. The capacitor values, C1 and C2, shown

in Figure 3 below were determined using a 25MHz, 18pF

Figure 3. CRYSTAL INPUt INTERFACE

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.

ICS84332

XTAL_IN

XTAL_OUT

18pF Parallel Cry stal

22p

INPUTS:

LVCMOS CONTROL PINS:

All control pins have internal pull-ups or pull-downs; additional

resistance is not required but can be added for additional

protection. A 1k

Ω resistor can be used.

RECOMMENDATIONS FOR UNUSED INPUT PINS

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