858012AK

www.icst.com/products/hiperclocks.html

REV. A NOVEMBER 28, 2005

9

Integrated

Circuit

Systems, Inc.

ICS858012

PRELIMINARY

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

50

Ω transmission lines. Matched impedance techniques should

be used to maximize operating frequency and minimize signal

distortion. Figures 5A and 5B 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.

V

50

Ω

50

Ω

RTT

Z

Z

FOUT

FIN

RTT =

Z

o

1

((V

3.3V

125

Ω

125

Ω

84

Ω

84

Ω

Z

Z

FOUT

FIN

All unused LVPECL outputs can be left floating. We recommend

that there is no trace attached. Both sides of the differential

output pair should either be left floating or terminated.