GS3590 datasheet(24/118 Pages) SEMTECH

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GS3590

Final Data Sheet Rev.4



PDS-061414 September 2017

24 of 118

Semtech

Proprietary & Confidential

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By default at power up or after system reset, the trace equalizer is configured to

compensate for up to 3" of 7mil strip-line in FR4 material at high-frequencies.

Note: Although not a requirement, launch swing of 800mVppd is recommended for

trace lengths longer than 5".

4.3.2 CD (Carrier Detect) and LOS (Loss of Signal)

LOS is the complement of CD and is used by various automatic control modes including

mute on LOS, which will be covered in the output section of this document.

The default settings of the Trace Equalizer Carrier Detection sub-block should satisfy

most applications; however the Carrier Detection mechanism in the Trace Equalizer is

highly-configurable and allows the system designer to optimize the sensitivity and

hysteresis of Carrier Detection mechanism to meet specific system requirements.

The trace equalizer Carrier Detect is reported by status parameter STAT_PRI_CD in

The first CD control parameter is CFG_TREQ0_CD_BOOST in register 0x1E. This

parameter determines the method and therefore the level of equalization to be used on

the input signal routed to the Carrier Detection sub-block. The default value is 0b, which

maximizes the level of equalization. Alternatively, the designer can choose to have this

signal equalized at the same level as the main signal routed to the CDR by setting

CFG_TREQ0_CD_BOOST to 1b. The setting of this parameter has no impact on the main

signal routed to the CDR.

The last two CD control parameters can be found in register 0x1F. Parameters

CFG_TREQ0_CD_ASSERT_THRESH and CFG_TRE0Q_CD_DEASSERT_THRESH set

the Carrier Detect assert and de-assert thresholds to the input signal, which also defines

the hysteresis of CD signal.

The default values of CFG_TREQ0_CD_ASSERT_THRESH and

CFG_TREQ0_CD_DEASSERT_THRESH are 4d and 3d respectively. With the default

settings, the minimum launch swing needed to assert the carrier detect is 200mV and it

will be de-asserted when the signal level falls below 150mV.

The STAT_PRI_CD (Carrier Detect) parameter will be set to 0b and the LOS will be set to

1b whenever a new signal at the input does not exceed the assert threshold, or an

existing signal falls below the de-assert threshold. The result is that the device will not

indicate lock, and the outputs will mute (assuming Mute on LOS is left to its default value

in the CONTROL_OUTPUT_MUTE register—0x49). See Section 4.8.7 for more details.

Given a differential input trace with 17dB of insertion loss at 1.485GHz and

CFG_TREQ_CD_BOOST = 0b, Figure 4-3 illustrates the relationship between launch

swing voltage, and minimum threshold setting to assert or de-asset Carrier Detect at all

rates up to threshold setting at 2.97Gb/s.

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