ICS843004AI01 datasheet(8/14 Pages) ICST

8 / 14 page

843004AGI-01

www.icst.com/products/hiperclocks.html

REV. A FEBRUARY 11, 2005

Integrated

Circuit

Systems, Inc.

ICS843004I-01

FEMTOCLOCKS™CRYSTAL-TO-

3.3V, 2.5V LVPECL FREQUENCY SYNTHESIZER

CRYSTAL INPUT INTERFACE

The ICS843004I-01 has been characterized with 18pF paral-

lel resonant crystals. The capacitor values shown in

Figure 4

Figure 4. CRYSTAL INPUt INTERFACE

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

nant crystal and were chosen to minimize the ppm error.

ICS843004I-01

33p

18pF Parallel Crystal

27p

XTAL_OUT

XTAL_IN

TERMINATION FOR 2.5V LVPECL OUTPUT

Figure 3A and Figure 3B show examples of termination for 2.5V

LVPECL driver. These terminations are equivalent to terminat-

ing 50

Ω to V

CC - 2V. For VCCO = 2.5V, the VCCO - 2V is very close to

ground level. The R3 in Figure 3B can be eliminated and the

termination is shown in

Figure 3C.

FIGURE 3C. 2.5V LVPECL TERMINATION EXAMPLE

Zo = 50 Ohm

VCCO=2.5V

Zo = 50 Ohm

2.5V

2,5V LVPECL

Driv er

FIGURE 3B. 2.5V LVPECL DRIVER TERMINATION EXAMPLE

VCCO=2.5V

Zo = 50 Ohm

2,5V LVPECL

Driv er

Zo = 50 Ohm

2.5V

FIGURE 3A. 2.5V LVPECL DRIVER TERMINATION EXAMPLE

62.5

2.5V

2,5V LVPECL

Driv er

250

Zo = 50 Ohm

62.5

2.5V

250

VCCO=2.5V

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