GS3590 datasheet(48/118 Pages) SEMTECH

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GS3590

Final Data Sheet Rev.4



PDS-061414 September 2017

48 of 118

Semtech

Proprietary & Confidential

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For example, if the CDR is locked to 3G, the following parameters will be used to control

the output drivers:

 CFG_OUTPUT1_TD_3G_DRIVER_SWING

 CFG_OUTPUT1_TD_3G_PREEMPH_WIDTH

 CFG_OUTPUT1_TD_3G_PREEMPH_AMPL

 CFG_OUTPUT1_TD_3G_PREEMPH_PWRDWN

Note: If per-rate settings are being used, when the CDR is not locked the trace driver will

use the Bypass trace driver output group settings.

4.8.5 Amplitude and Pre-Emphasis Control

The two output drivers offer very granular amplitude and pre-emphasis control. For

optimal loss compensation, both the pre-emphasis pulse amplitude and the

pre-emphasis pulse width can be independently configured on both output drivers.

This extra flexibility provides a mechanism to better shape the pre-emphasis gain to

match the frequency loss response of interconnect composed of trace, connector and

via losses. The swing and pre-emphasis can be independently configured for specific

data rates.

Note: Output 0 references the Cable Driver, and Output 1 references the Trace Driver.

The output swing on the Cable Driver can be configured for the following three rate

groups:

CFG_OUTPUT0_CD_SD_DRIVER_SWING (MADI and SD)

CFG_OUTPUT0_CD_HD_DRIVER_SWING (HD and 3G)

CFG_OUTPUT0_CD_BYPASS_DRIVER_SWING (Bypass)

The output pre-emphasis on the Cable Driver can be configured for the following two

rate groups:

CFG_OUTPUT0_CD_HD_PREEMPH_WIDTH (HD and 3G)

CFG_OUTPUT0_CD_HD_PREEMPH_AMPL (HD and 3G)

CFG_OUTPUT0_CD_BYPASS_PREEMPH_WIDTH (Bypass)

CFG_OUTPUT0_CD_BYPASS_PREEMPH_AMPL (Bypass)

The output driver swing and pre-emphasis will use the rate specific swing configuration

when the CDR is locked to that rate. The default swing setting is 800mVpp single-ended

into an external 75Ω load. The swing can be adjusted in ~20mV increments. The Cable

Driver supply is pin 25 (VCCO_0) and should be connected to a 2.5V supply. The default

pre-emphasis settings provide minimal insertion loss compensation.

The Trace Driver amplitude can be configured to use the same swing for all rates, or

similarly to the Cable Driver, can have a specific swing for each rate.

The following registers allow a per rate swing to be configured for 4 rates:

CFG_OUTPUT1_TD_SD_DRIVER_SWING (SD)

CFG_OUTPUT1_TD_HD_DRIVER_SWING (HD)

CFG_OUTPUT1_TD_3G_DRIVER_SWING (3G)

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CFG_OUTPUT1_TD_BYPASS_DRIVER_SWING (Bypass)

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