GS12341 datasheet(16/109 Pages) SEMTECH

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GS12341

Final Data Sheet

Rev.1

PDS-061928

August 2019

16 of 109

Semtech

Proprietary & Confidential

www.semtech.com

4.2 Cable Equalizer

The GS12341 can automatically adjust its gain to equalize and restore SMPTE compliant

signals received over different lengths of coaxial cable having loss characteristics similar

to Belden 1694A, 4964R, or Canare L-5.5CUHD. With the default settings, the device will

automatically equalize MADI at 125Mb/s and SMPTE compliant signals between SD at

270Mb/s and UHD-SDI at 11.88Gb/s and bypass signals below 125Mb/s.

The

GS12341 featuresprogrammableLaunchSwingCompensation, squelch threshold

adjust, and bypass, all of which can be set through the device's host interface. The

equalized or bypassed signal is then routed to the eye monitor and serial digital

Reclocker block.

4.2.1 Cable Equalizer Bypass

With the default settings, the device will automatically bypass signals below 125Mb/s.

During cable equalizer-bypass mode, the device supports low data rate and slow edge

signals such as SMPTE310 and AES3id. The rise/fall times must not exceed 62ns. While in

cable equalizer bypass mode, signal will not be reclocked.

To force the device to bypass the cable equalizer, DC restoration stage, and Reclocker,

the following two methods can be used:

Host Interface Control:



Set the following parameters in register 17h:

•CTRL_CEQ_AUTO_BYPASS = 0

•

CTRL_CEQ_MANUAL_BYPASS = 1

GPIO Control:

1. Configure a GPIO as an input by writing 0h to the CFG_GPIO<n>_OUTPUT_ENA.

2. Configure the GPIO function as “cable equalizer bypass enable,” by writing 84h to

CFG_GPIO<n>_FUNCTION.

3. Drive the selected GPIO pin HIGH.

Note: The <n> in the control parameter names refers to the GPIO pin number.

4.2.2 Upstream Launch Swing Compensation

The GS12341 cable equalizer has an automatic gain control circuit, that is optimized on

the assumption that the trace driver in the upstream device is SMPTE compliant and has

a launch swing of 800mVpp ±10%. When the source amplitude is known to be

non-SMPTE compliant, a compensation adjustment can be made in the GS12341. The

GS12341 can adjust for launch swings in the range of 250mV to 1V in approximately

50mVppd increments. Upstream launch swing compensation can be adjusted through

the CFG_EQ_INPUT_LAUNCH_SWING_COMP parameter in control register 0x18. The

default parameter value is 80d (50h), which corresponds to a nominal launch swing of

800mVppd.

GS12341 Datasheet(PDF) 16 Page - Semtech Corporation

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