ICS40004AI01 datasheet(10/16 Pages) IDT

10 / 16 page

840004AGI-01

REV. A OCTOBER 22, 2007

ICS840004I-01

FEMTOCLOCKS™CRYSTAL-TO-

LVCMOS/LVTTL FREQUENCY SYNTHESIZER

APPLICATION INFORMATION

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

are vulnerable to random noise. The ICS840004I-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

CRYSTAL INPUT INTERFACE

The ICS840004I-01 has been characterized with 18pF paral-

lel resonant crystals. The capacitor values shown in Figure 2

FIGURE 2. CRYSTAL INPUt INTERFACE

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

nant crystal and were chosen to minimize the ppm error.

ICS84332

XTAL_IN

XTAL_OUT

18pF Parallel Cry stal

22p

ICS840004I-01

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