8535-31 Ver la hoja de datos (PDF) - Integrated Device Technology

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componentes Descripción

Fabricante

8535-31

LOW SKEW, 1-TO-4, CRYSTAL OSCILLATOR/LVCMOS-TO-3.3V LVPECL FANOUT BUFFER

Integrated Device Technology 

Integrated

ICS8535-31

ICS8535-31

L S , 1- -4, C O / LOW SKEW,

Circuit

1-TOS-4y, sCtRemYSsT, IAnLcO. SCILLATOR/

LVCMOS-TO-3.3V

LVPOEWCL

FKAENWOUT

BUTOFFER

LVCMOS- -3.3V LVPECL F B TO

RYSTAL SCILLATORTSD

ANOUT UFFER

APPLICATION INFORMATION

TERMINATION FOR LVPECL OUTPUTS

The clock layout topology shown below is a typical termina-

tion for LVPECL outputs. The two different layouts mentioned

are recommended only as guidelines.

FOUT and nFOUT are low impedance follower outputs that gen-

erate ECL/LVPECL compatible outputs.Therefore, terminating

resistors (DC current path to ground) or current sources must

be used for functionality. These outputs are designed to drive

50Ω transmission lines. Matched impedance techniques should

be used to maximize operating frequency and minimize signal

distortion. Figures 2A and 2B show two different layouts which

are recommended only as guidelines. Other suitable clock lay-

outs may exist and it would be recommended that the board

designers simulate to guarantee compatibility across all printed

circuit and clock component process variations.

Zo = 50Ω

FOUT

FIN

Zo = 50Ω

50Ω

RTT =

1

((VOH + VOL) / (VCC – 2)) – 2

Zo

50Ω

VCC - 2V

RTT

FOUT

3.3V

125Ω

125Ω

Zo = 50Ω

FIN

Zo = 50Ω

84Ω

84Ω

FIGURE 2A. LVPECL OUTPUT TERMINATION

FIGURE 2B. LVPECL OUTPUT TERMINATION

CRYSTAL INPUT INTERFACE

The ICS8535-31 has been characterized with 18pF parallel

resonant crystals. The capacitor values, C1 and C2, shown

in Figure 3 below were determined using an 18pF parallel reso-

nant crystal and were chosen to minimize the ppm error.

These same capacitor values will tune any 18pF parallel reso-

nant crystal over the frequency range and other parameters

specified in this data sheet. The optimum C1 and C2 values

can be slightly adjusted for different board layouts.

X1

18pF Parallel Crystal

XTAL_IN

C1

18p

XTAL_OUT

C2

22p

Figure 3. CRYSTAL INPUt INTERFACE

8535AG-31

www.icst.com/products/hiperclocks.html

8

IDT™ / ICS™ LOW SKEW, 1-TO-4, CRYSTAL OSCILLATOR/ LVCMOS-TO-3.3V LVPECL FANOUT BUFFER

8

REV. B APRIL 29, 2005

ICS8535-31

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