GS3490 Datasheet, PDF (13/22 Pages) Semtech Corporation – Configurable Adaptive Cable Equalizer/Cable Driver

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.
Table 4-1: GS3490 Operating Modes
EQ_DISABLE
CD_ENABLE
Description
0
0
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 75Ω load that
is not driving a 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.
GS3490
Final Data Sheet
GENDOC-058568
Rev. 1
April 2014
www.semtech.com
13 of 22
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