GS3490

Final Data Sheet

Rev. 1

GENDOC-058568

April 2014

13 of 22

Proprietary & Confidential

www.semtech.com

4. Detailed Description

The GS3490 is a half-duplex, bi-directional device that integrates the functions of both

a cable equalizer and a cable driver in one package, allowing for a single application

circuit to perform both functions through a single BNC connector. The GS3490 pin out

enables switching from one mode to another using a single logic control signal.

4.1 Equalizer Mode

4.1.1 Equalizer Mode Enable

To enable Equalizer Mode, both the EQ_DISABLE and CD_ENABLE pins must be set to

logic LOW. These two pins may be tied together and controlled from a single logic

signal.

4.1.2 Serial Digital Inputs (SDI/SDI)

Please refer to Section 5.1 for the correct way to implement the bi-directional serial

input/output. Other application circuits are not supported.

4.1.3 Automatic (Adaptive) Cable Equalization

The GS3490 automatically adjusts its gain to equalize and restore signals received over

different lengths of coaxial cable having loss characteristics similar to Belden 8281 or

1694A. The device is designed to automatically equalize SMPTE SDI signal rates from

125Mb/s up to 2.97Gb/s and DVB-ASI signals at 270Mb/s.

The equalized signal is DC-restored, effectively restoring the logic threshold of the

equalized signal to its correct level independent of shifts due to AC-coupling.

Adaptive Cable Equalization and DC Restoration can be disabled by pulling the

EQ_BYPASS pin HIGH.

Table 4-1: GS3490 Operating Modes

EQ_DISABLE

CD_ENABLE

Description

00

Equalizer Mode

0

1

Debug Mode*

1

0

Power-Down Mode

1

1

Cable Driver Mode

*Note: Data represented at the Cable Driver’s digital data input is passed through the device,

looped back through the Equalizer and appears on the Equalizer’s digital data output. The

data is looped through the device, provided the SDI/O BNC is terminated with a 75

Ω load that

is not driving a signal.