ICS843004 datasheet(10/16 Pages) ICST

10 / 16 page

843004AG

www.icst.com/products/hiperclocks.html

REV. A NOVEMBER 18, 2004

Integrated

Circuit

Systems, Inc.

ICS843004

FEMTOCLOCKS™LVCMOS/CRYSTAL-TO-

3.3V LVPECL FREQUENCY SYNTHESIZER

CRYSTAL INPUT INTERFACE

The ICS843004 has been characterized with 18pF parallel

resonant crystals. The capacitor values shown in

Figure 3

Figure 3. CRYSTAL INPUt INTERFACE

below were determined using a 26.5625MHz 18pF parallel

resonant crystal and were chosen to minimize the ppm error.

ICS843004

33p

18pF Parallel Crystal

27p

XTAL_OUT

XTAL_IN

Zo = 50 Ohm

ICS843004

133

VCC

27pF

RU1

0.1u

To Logic

Input

pins

VCCO=3.3V

33pF

Set Logic

Input to

'1'

0.1u

Zo = 50 Ohm

133

0.01u

Set Logic

Input to

'0'

To Logic

Input

pins

VCCA

25MHz

10uF

VCC

RD2

VCC=3.3V

0.1u

82.5

18pF

RU2

Not Install

VDD

133

3.3V

VDD

R10

82.5

Zo = 50 Ohm

133

VCCO

Logic Control Input Examples

82.5

RD1

Not Install

Zo = 50 Ohm

3.3V

0.1u

LAYOUT GUIDELINE

Figure 4 shows a schematic example of the ICS843004. An ex-

ample of LVEPCL termination is shown in this schematic. Addi-

tional LVPECL termination approaches are shown in the LVPECL

Termination Application Note. In this example, an 18pF parallel

FIGURE 4. ICS843004 SCHEMATIC EXAMPLE

resonant 26.5625MHz crystal is used. The C1=27pF and

C2=33pF are recommended for frequency accuracy. For differ-

ent board layout, the C1 and C2 may be slightly adjusted for

optimizing frequency accuracy.

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