ICS843003 datasheet(10/17 Pages) ICST

10 / 17 page

843003AG

www.icst.com/products/hiperclocks.html

REV. A JULY 27, 2004

Integrated

Circuit

Systems, Inc.

ICS843003

FEMTOCLOCKS™CRYSTAL-TO-3.3V LVPECL

FREQUENCY SYNTHESIZER

APPLICATION INFORMATION

CRYSTAL INPUT INTERFACE

The ICS843003 has been characterized with 18pF parallel

resonant crystals. The capacitor values shown in

Figure 3

below were determined using a 31.25MHz or 26.041666MHz

Figure 3. CRYSTAL INPUt INTERFACE

18pF parallel resonant crystal and were chosen to minimize

the ppm error.

ICS843003

POWER SUPPLY FILTERING TECHNIQUES

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

are vulnerable to random noise. The ICS843003 provides sepa-

rate power supplies to isolate any high switching

noise from the outputs to the internal PLL. V

CC, VCCA, and VCCOx

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.

FIGURE 2. POWER SUPPLY FILTERING

Ω

CCA

µF

.01

µF

3.3V

.01

µF

33p

18pF Parallel Crystal

27p

XTAL_OUT

XTAL_IN

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