ICS421004AI01 datasheet(8/13 Pages) ICST

8 / 13 page

8421004AGI-01

www.icst.com/products/hiperclocks.html

REV. A MACH 29, 2005

Integrated

Circuit

Systems, Inc.

ICS8421004I-01

FEMTOCLOCKS™CRYSTAL-TO-

HSTL FREQUENCY SYNTHESIZER

PRELIMINARY

CRYSTAL INPUT INTERFACE

The ICS8421004I-01 has been characterized with 18pF par-

allel resonant crystals. The capacitor values shown in

Figure

Figure 2. CRYSTAL INPUt INTERFACE

2 below were determined using a 25MHz 18pF parallel reso-

nant crystal and were chosen to minimize the ppm error.

ICS8421004I-01

APPLICATION INFORMATION

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

are vulnerable to random noise. The ICS8421004I-01 provides

separate power supplies to isolate any high switching

noise from the outputs to the internal PLL. V

DD, VDDA, and VDDO

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 10

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

capacitor should be connected to each V

DDA.

POWER SUPPLY FILTERING TECHNIQUES

FIGURE 1. POWER SUPPLY FILTERING

DDA

μF

.01

μF

3.3V or 2.5V

.01

μF

22p

18pF Parallel Crystal

22p

XTAL_OUT

XTAL_IN

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