GS3281 datasheet(15/97 Pages) SEMTECH

15 / 97 page

GS3281

Final Data Sheet

Rev.7

PDS-061453

January 2019

15 of 97

Semtech

Proprietary & Confidential

www.semtech.com

4. Detailed Description

4.1 Device Description

The GS3281 is a dual output SMPTE compliant re-timing cable driver with integrated

75Ω internal terminations. It includes a 100Ω differential trace equalizer to receive the

outgoing signal from the system. The Trace Equalizer has offset correction and boost

control, which can compensate for 17dB of insertion loss at 1.485GHz. The device

includes a CDR which will lock to and retime valid SMPTE signals to produce extremely

low output jitter, even at extended trace lengths. The CDR has extensive loop

bandwidth control to enable jitter transfer optimization. To facilitate system testing, the

device also includes 3D eye monitor, PRBS7 checker and generator. The Cable Driver has

amplitude and pre-emphasis control to compensate for significant insertion loss

between device output and BNC. The pre-emphasis control is two dimensional, where

both pre-emphasis pulse amplitude and width adjustments can be made to help

optimize for interconnect mismatches such as vias and connectors.

Note: The parameters referred to within Section 4.2.1 to Section 4.2.2 are linked to their

respective registers in Table 4-1. For a complete list of registers and functions, please see

Section 5.

4.1.1 Sleep Mode

To enable low power operation, the GS3281 has manual and automatic sleep mode

control.

The default mode is automatic sleep mode on LOS (Loss of signal). The device can also

be manually put into sleep mode. When the device is in sleep mode, all the core blocks

are powered-down, except the host interface and carrier detect circuits. The cable driver

can be configured to be disabled or muted during sleep.

The CTRL_AUTO_SLEEP and CTRL_MANUAL_SLEEP parameters in register 0x3,

control the sleep mode of the device. The default value of the CTRL_AUTO_SLEEP

parameter is 1b (auto sleep). While in auto sleep mode, the CTRL_MANUAL_SLEEP

parameter has no effect. To enable host control of the sleep mode, set the

CTRL_AUTO_SLEEP parameter to 0b manual sleep control. To prevent the device from

entering sleep, set the CTRL_MANUAL_SLEEP parameter to 0b (not sleep). To manually

configure the device to sleep, set the CTRL_MANUAL_SLEEP parameter to 1b (sleep).

The device can also be manually made to sleep through the GPIO pins. The default GPIO

pin to control sleep is GPIO2 (pin 33). Drive this pin HIGH to make the device sleep.

Section 4.6 describes the PRBS generator function. If the device's PRBS generator is

intended to be used without a valid input signal, the device should be manually set to

not sleep as described above. Without a valid input signal, an LOS status will be

generated and the device will enter sleep mode and the PRBS block will be disabled. For

a description of LOS thresholds and settings, see Section 4.2.2.

GS3281 Datasheet(PDF) 15 Page - Semtech Corporation

GS3281 Datasheet(HTML) 15 Page - Semtech Corporation

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