GS3470 datasheet(26/169 Pages) SEMTECH

26 / 169 page

GS3470

Final Data Sheet

Rev.8

PDS-060500

September 2017

26 of 169

Semtech

www.semtech.com

4.3.4 DVB-ASI Mode

When in DVB-ASI mode (SMPTE_BYPASS = LOW and DVB_ASI = HIGH), the retimer PLL

locks to a DVB-ASI stream. In DVB-ASI mode, the parallel outputs are configured

appropriately as described in 4.9.3 Parallel Output in DVB-ASI Mode. None of the SMPTE

detection and processing functions are available in this mode.

4.4 Digital Differential Input (DDI/DDI)

The GS3470 can accept two serial digital inputs compliant with SMPTE ST 424, SMPTE

292, and SMPTE ST 259-C– however, only one of the input serial data streams can be

retimed. The GS3470 contains a 100Ω differential input buffer which can be DC-coupled

to Semtech equalizers, but only if equalizer output stage is connected to 1.2V.

Otherwise must be AC coupled.

See Figure 4-1for a visualization of the Flex Input Loopback.

INPUT_CONFIG[3:2] allows for selection of DDI0 or DDI1 into the parallel retimed

output and DDO path.

LOS_CTRL[8] register contains the LOS_AFE_SEL bit, which allows for selection of DDI0

or DDI1 for LOS sensing.

4.5 Serial Digital Loop-Through Output

The GS3470 contains a differential serial digital output buffer. This output provides an

active loop-through of the input signal. It can be a reclocked or non-reclocked version

of the input used for processing or a non-reclocked version of the other input. Moreover,

selection of the loop-through output is independent of the selection of the signal going

into the de-serializer block.

Table 4-3 provides a summary of all the options available for the serial digital output.

The DDO, DDO differential signal is capable of driving a Semtech Cable Driver through

at least 150mm of 100Ω differential FR4 trace, such that the Cable Driver output

conforms to the relevant SMPTE specification for the data rate, with the exception of the

jitter specifications.

The output can be DC-coupled into Semtech Cable Drivers that support 1.2V, 1.8V and

2.5V inputs.

The output buffer may be disabled to achieve power savings. This can be done using the

SERIAL_LOOPBACK_EN bit through the GSPI interface.

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