GS3241 datasheet(39/108 Pages) SEMTECH

39 / 108 page

GS3241

Final Data Sheet

Rev.2

PDS-061444

September 2017

39 of 108

Semtech

Proprietary & Confidential

www.semtech.com

4.7 Output Drivers

The GS3241 features two independently-configurable output drivers (see Figure 3-3),

with data (re-timed or bypassed) available on both outputs. The two drivers provide

highly-configurable amplitude and pre-emphasis control. The signal on the outputs can

be inverted to help with signal polarity when layout requires trace inversion. The PRBS

generator is available on both outputs. The LOS (Loss Of Signal) status from the

equalizer stage can be used to automatically mute or disable the outputs on their

assertion. The Loss of Lock status from the CDR block can be used to mute the outputs.

The trace drivers can be configured to mute or disable during sleep. The sleep control

modes takes precedence over the manual or automatic LOS and Loss of Lock output

control modes.

Note: The <n> in the control parameter names refers to the output number. Output 0 is

the trace driver output DDO0 and output 1 is the trace driver output DDO1.

4.7.1 Bypassed Re-timer Signal Output Control

With the default power-up settings, the GS3241 outputs will automatically switch to the

bypassed signal (non-re-timed) whenever the PLL is unlocked. Alternatively, manual

re-timer bypass may be configured by setting the CTRL_OUTPUT<n>_RETIMER_

AUTO_BYPASS and CTRL_OUTPUT<n>_RETIMER_MANUAL_BYPASS parameters in

remain bypassed for all rates.

The re-timer bypass function, manual or automatic, does not affect the input

equalization function of the device.

If both outputs are manually disabled, then the device will power down the CDR block

and features of the re-timer such as rate detect and lock detect will no longer be

accessible in this mode.

4.7.2 Output Driver Polarity Inversion

While in data mode, the signal polarity may be inverted at the outputs through the

CTRL_OUTPUT<n>_ DATA_ INVERT parameters in register 0x48. This may be useful to

compensate for an inverted upstream signal or to facilitate board signal routing. To

invert the polarity of either of the two output drivers, write 1b to control parameter

CTRL_OUTPUT<n>_DATA_ INVERT.

4.7.3 Output Driver Data Rate Selection

By default, the GS3241 uses the SD trace driver output group settings for all data rates,

regardless of CDR lock condition or data rate being applied. The following parameters

are used to control the output for all data rates in the default condition:

 CFG_OUTPUT<n>_TD_SD_DRIVER_SWING

 CFG_OUTPUT<n>_TD_SD_PREEMPH_WIDTH

 CFG_OUTPUT<n>_TD_SD_PREEMPH_AMPL

 CFG_OUTPUT<n>_TD_SD_PREEMPH_PWRDWN

GS3241 Datasheet(PDF) 39 Page - Semtech Corporation

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