ICS840004 datasheet(10/13 Pages) ICST

10 / 13 page

Integrated

Circuit

Systems, Inc.

8400042AG

www.icst.com/products/hiperclocks.html

REV. A SEPTEMBER 16, 2004

ICS840004

FEMTOCLOCKS™CRYSTAL-TO-

LVCMOS/LVTTL FREQUENCY SYNTHESIZER

PRELIMINARY

APPLICATION INFORMATION

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

are vulnerable to random noise.The ICS840004 provides sepa-

rate 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

Ω

DDA

µF

.01

µF

3.3V

.01

µF

CRYSTAL INPUT INTERFACE

The ICS840004 has been characterized with 18pF parallel reso-

nant crystals.The capacitor values shown in

Figure 2 below were

Figure 2. CRYSTAL INPUt INTERFACE

determined using a 26.5625MHz 18pF parallel resonant crystal and

were chosen to minimize the ppm error.

ICS84332

XTAL_IN

XTAL_OUT

18pF Parallel Cry stal

22p

ICS840004

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