GS3281 datasheet(40/97 Pages) SEMTECH

40 / 97 page

GS3281

Final Data Sheet

Rev.7

PDS-061453

January 2019

40 of 97

Semtech

Proprietary & Confidential

www.semtech.com

4.7.4.1 Pre-Emphasis Optimization

The goal of pre-emphasis is to open the eye at the downstream receiver as much as

possible. This means minimizing ISI jitter while meeting sufficient inner eye amplitude

to meet a receiver's input sensitivity. The cable driver has the additional requirement to

meet the SMPTE output specification.

The GS3281 has a high level of precision for pre-emphasis control, which allows for fine

optimization of any loss channel. The default cable driver settings should meet SMPTE

output specification for most applications with short (1 to 2 inch) trace between the

GS3281 and the output BNC. However, the pre-emphasis values may be adjusted to

produce a better-looking eye. It is difficult to provide guidance regarding dB, as a 3G eye

diagram looks different depending on the video test equipment used. The designer

must optimize for their targets.

Table 4-8: Output Swing and Pre-Emphasis Control Parameters

Addressh

Parameter Name

Description

0x2B/0x29,

OUTPUT_ PARAM_CD_

SD_3/

OUTPUT_ PARAM_CD_

SD_1

CFG_OUTPUT<n>_CD_

SD_DRIVER_SWING

Output amplitude configuration parameter.

<n> = 0: For SD and MADI rates on SDO0.



<n> = 1: For SD and MADI rates on SDO1.

0x2D/0x2F

OUTPUT_ PARAM_

CD_HD_1/

OUTPUT_ PARAM_

CD_HD_3

CFG_OUTPUT<n>_CD_

HD_DRIVER_SWING

Output amplitude configuration parameter.

<n> = 0: For HD and 3G rates on SDO0.



<n> = 1: For HD and 3G rates on SDO1.

0x2C/0x2E

OUTPUT_ PARAM_

CD_HD_0/

OUTPUT_ PARAM_

CD_HD_2

CFG_OUTPUT<n>_CD_HD_

PREEMPH_WIDTH

Output pre-emphasis pulse width configuration parameter.

<n> = 0: For HD and 3G rates on SDO0.



<n> = 1: For HD and 3G rates on SDO1.

CFG_OUTPUT<n>_CD_HD_

PREEMPH_PWRDWN

Output pre-emphasis power down configuration parameter.

<n> = 0: For HD and 3G rates on SDO0.



<n> = 1: For HD and 3G rates on SDO1.

CFG_OUTPUT<n>_CD_HD_

PREEMPH_AMPL

Output pre-emphasis pulse amplitude configuration parameter.

<n> = 0: For HD and 3G rates on SDO0.



<n> = 1: For HD and 3G rates on SDO1.

0x31/0x33

OUTPUT_ PARAM_

CD_BYPASS_1/

OUTPUT_ PARAM_

CD_BYPASS_3

CFG_OUTPUT<n>_CD_BYPASS_

DRIVER_SWING

Output amplitude configuration parameter.

<n> = 0: For Bypass on SDO0.



<n> = 1: For Bypass on SDO1.

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