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ICS844002AG REV. A SEPTEMBER 28, 2007

ICS844002

FEMTOCLOCKS™ CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER

The ICS844002 has been characterized with 18pF parallel

resonant crystals. The capacitor values shown in Figure 2 below

were determined using a 26.5625MHz, 18pF parallel resonant

crystal and were chosen to minimize the ppm error.

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

are vulnerable to random noise. The ICS844002 provides sepa-

rate power supplies to isolate any high switching noise from

the outputs to the internal PLL. V

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

0.01

μF bypass capacitor should be connected to each V

10

Ω

V

DDA

10

μF

.01

μF

3.3V or 2.5V

.01

μF

V

DD

C1

33p

X1

18pF Parallel Crystal

C2

27p

XTAL_OUT

XTAL_IN