853054AL datasheet(9/15 Pages) ICST

9 / 15 page

Integrated

Circuit

Systems, Inc.

853054AG

www.icst.com/products/hiperclocks.html

REV. A JANUARY 5, 2006

ICS853054

4:1, DIFFERENTIAL-TO-3.3V OR 2.5V

LVPECL/ECL CLOCK MULTIPLEXER

PRELIMINARY

CC - 2V

RTT

o = 50Ω

FOUT

FIN

RTT =

((V

OH + VOL) / (VCC – 2)) – 2

3.3V

125

o = 50Ω

FOUT

FIN

The clock layout topology shown below is a typical termi-

nation for LVPECL outputs. The two different layouts men-

tioned are recommended only as guidelines.

FOUT and nFOUT are low impedance follower outputs that

generate ECL/LVPECL compatible outputs. Therefore, termi-

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

must be used for functionality. These outputs are designed to

drive 50

Ω transmission lines. Matched impedance techniques

should be used to maximize operating frequency and mini-

mize signal distortion. Figures 3A and 3B show two different

layouts which are recommended only as guidelines. Other

suitable clock layouts may exist and it would be recommended

that the board designers simulate to guarantee compatibility

across all printed circuit and clock component process varia-

tions.

FIGURE 3B. LVPECL OUTPUT TERMINATION

FIGURE 3A. LVPECL OUTPUT TERMINATION

TERMINATION FOR 3.3V LVPECL OUTPUTS

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