ICS002AI40L datasheet(14/23 Pages) IDT

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ICS843002I-40

175MHZ, FEMTOCLOCKS™ VCXO BASED SONET/SDH JITTER ATTENUATOR

IDT™ / ICS™ VCXO BASED SONET/SDH JITTER ATTENUATOR

ICS843002AKI-40 REV. A NOVEMBER 7, 2007

Termination for 3.3V LVPECL Outputs

The clock layout topology shown below is a typical termination for

LVPECL outputs. The two different layouts mentioned are

recommended only as guidelines.

FOUT and nFOUT are low impedance follower outputs that

generate 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 layouts may

exist and it would be recommended that the board designers

simulate to guarantee compatibility across all printed circuit and

clock component process variations.

Figure 5A. 3.3V LVPECL Output Termination

Figure 5B. 3.3V LVPECL Output Termination

CC - 2V

Ω

RTT

o = 50Ω

FOUT

FIN

RTT =

((V

OH + VOL) / (VCC – 2)) – 2

3.3V

125

Ω

125

Ω

o = 50Ω

FOUT

FIN

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