GS3440 Adaptive Cable Equalizer

Final Data Sheet

Rev. 2

December 2012

17 of 23

Proprietary and Confidential

5. Application Information

5.1 High-Gain Adaptive Cable Equalizers

The GS3440 is a multi-rate adaptive cable equalizer. In order to continue to extend the

cable length that the device can support, it is necessary to have high-gain in the

equalizer.

A video cable equalizer must provide wide band gain over a range of frequencies in

order to accommodate the range of data rates and signal patterns that are present in a

SMPTE-compliant serial video stream.

Small levels of signal or noise present at the input pins of the equalizer may cause

chatter at the output. In order to prevent this from happening, particular attention must

be paid to board layout.

5.2 PCB Layout

Special attention must be paid to component layout when designing Serial Digital

Interfaces for HDTV. An FR-4 dielectric can be used, however, controlled impedance

transmission lines are required for PCB traces longer than approximately 1cm. Note the

following PCB artwork features used to optimize performance:

• PCB trace width for 3Gb/s rate signals is closely matched to SMT component width

to minimize reflections due to change in trace impedance.

• High-speed traces are curved to minimize impedance changes.

• Cutouts in the inner layers should be used under the GS3440 input and output

components to minimize parasitic capacitance. For more detail on this and other

layout recommendations, please refer to A Guide For Designing With Gennum’s

3G-SDI Equalizers.