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©2016 Integrated Device Technology, Inc.

Revision B, February 18, 2016

85311I Datasheet

Recommendations for Unused Output Pins

Outputs:

LVPECL Outputs

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.

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.

The differential outputs 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



transmission lines. Matched impedance techniques should be used

to maximize operating frequency and minimize 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 variations.

Figure 3A. 3.3V LVPECL Output Termination

Figure 3B. 3.3V LVPECL Output Termination

R1

84



R2

84



3.3V

R3

125



R4

125



Z

o = 50

Z

o = 50

Input

3.3V

3.3V

+

_