ICS843252 Просмотр технического описания (PDF) - Integrated Circuit Systems

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ICS843252

FEMTOCLOCKS™ CRYSTAL-TO-3.3V LVPECL FREQUENCY SYNTHESIZER

Integrated Circuit Systems 

Integrated

Circuit

Systems, Inc.

PRELIMINARY

ICS843252

FEMTOCLOCKS™CRYSTAL-TO-3.3V LVPECL

FREQUENCY SYNTHESIZER

APPLICATION INFORMATION

POWER SUPPLY FILTERING TECHNIQUES

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

are vulnerable to random noise. The ICS843252 provides sepa-

rate power supplies to isolate any high switching

noise from the outputs to the internal PLL. VCC, VCCA, and VCCO_X

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 1 illustrates how

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

capacitor should be connected to each VCCA pin.

V

CC

V

CCA

3.3V

.01μF 10 Ω

.01μF

10μF

FIGURE 1. POWER SUPPLY FILTERING

CRYSTAL INPUT INTERFACE

The ICS843252 has been characterized with 18pF parallel reso-

nant crystals. The capacitor values shown in Figure 2 below

were determined using a 19.53125 or 25MHz, 18pF parallel

resonant crystal and were chosen to minimize the ppm error.

X1

18pF Parallel Crystal

XTAL_OUT

C1

22p

XTAL_IN

C2

22p

Figure 2. CRYSTAL INPUt INTERFACE

843252AG

www.icst.com/products/hiperclocks.html

9

REV. A NOVEMBER 9, 2005

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