GS12090 datasheet(47/121 Pages) SEMTECH

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GS12090

Final Data Sheet

Rev.9



PDS-061188

November 2018

47 of 121

Semtech

Proprietary & Confidential

www.semtech.com

4.8 Output Drivers

The GS12090 features two independent output drivers (see Figure 3-2 and Figure 3-3),

with data and PRBS Generators available on both outputs. The two drivers provide

highly-configurable amplitude and pre-emphasis control. The Cable Driver output on

SDIO can compensate for significant loss between the device output and BNC. The Trace

Driver, DDO, can compensate for up 15dB of insertion loss at 5.94GHz. This can represent

up to 20" of compensation at 12G for typical micro-strip and strip-line routing. In normal

operation, re-timed and bypassed data is available at both outputs. The signal on the

outputs can be inverted to help with signal polarity when layout requires trace

inversion. The PRBS Generator is available at 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 Cable Driver is always disabled during sleep, while the Trace

Driver 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 cable driver output SDIO and output 1 is the trace driver output DDO.

4.8.1 Bypassed Re-timer Signal Output Control

With the default power-up settings, the GS12090 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 register 0x4C to 0b

and 1b respectively via the host interface, in which case the PLL will remain bypassed for

all rates.

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

equalization function of the device.

If the GS12090 is in Cable Driver Mode, and loop-back is not enabled, then setting SDIO

to manual bypass 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. The same is true if

the GS12090 is in Cable Equalizer Mode and DDO is set to manual bypass.

4.8.2 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.

GS12090 Datasheet(PDF) 47 Page - Semtech Corporation

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