LMH0346

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SNLS248J – APRIL 2007 – REVISED APRIL 2013

DEVICE DESCRIPTION

The LMH0346 3 Gbps HD/SD SDI Reclocker is used in many types of digital video signal processing equipment.

Supported serial digital video standards are SMPTE 259M (C), SMPTE 292M, and SMPTE 424M. Corresponding

serial data rates are 270 Mbps, 1.483 Gbps, 1.485 Gbps, 2.967 Gbps, and 2.97 Gbps. DVB-ASI data at 270

Mbps may also be retimed. The LMH0346 retimes the serial data stream to suppress accumulated jitter. It

provides two low-jitter, differential, serial data outputs. The second output may be selected to output either serial

data or a low-jitter serial data-rate clock. Controls and indicators are: serial clock or second serial data output

select, manual rate select input, SD/HD rate output, lock detect output, auto/manual data bypass and output

mute.

Serial data inputs are CML and LVPECL compatible. Serial data and clock outputs are differential CML and

produce LVPECL compatible levels. The output buffer design can drive AC or DC-coupled, terminated 100

Ω

differential loads. The differential output level is 750 mVP-P into 100Ω AC or DC-coupled differential loads. Logic

inputs and outputs are LVCMOS compatible.

The device package is a 20-pin HTSSOP or a 24-pin WQFN. Both package options have an exposed die attach

pad. The exposed die attach pad is electrically connected to device ground (VEE) and is the negative electrical

terminal for the device. This terminal must be connected to the negative power supply or circuit ground.

Serial Data Inputs, Serial Data and Clock Outputs

SERIAL DATA INPUT AND OUTPUTS

The differential serial data input, SDI, accepts serial digital video data at the rates specified in Table 1. The serial

data input is differential LVPECL compatible. The input is intended to be DC interfaced to devices such as the

LMH0344 adaptive cable equalizer. The input is not internally terminated or biased. The input may be AC-

coupled if a suitable input bias voltage is provided. Figure 3 shows the equivalent input circuit for SDI and SDI.

The LMH0346 has two, retimed, differential, serial data outputs, SDO and SCO/SDO2. These outputs provide

low jitter, differential, retimed data to devices such as the LMH0302 cable driver. Output SCO/SDO2 is

multiplexed and can provide either a second serial data output or a serial clock output. Figure 4 shows the

equivalent output circuit for SDO, SDO, SCO/SDO2, and SCO/SDO2.

The SCO_EN input controls the operating mode for the SCO/SDO2 output. When the SCO_EN input is high the

SCO/SDO2 output provides a serial clock. When SCO_EN is low, the SCO/SDO2 output provides retimed serial

data.

Both differential serial data outputs, SDO and SCO/SDO2, are muted when the OUTPUT MUTE input is a logic

low level. SCO/SDO2 also mutes when the Bypass mode is activated and this output is operating as the serial

clock output (SCO_EN input is high). When muted, SDO and SDO (or SDO2 and SDO2) will assume opposite

differential output levels. The CML serial data outputs are differential LVPECL compatible. These outputs have

internal 50

Ω pull-ups and are suitable for driving AC or DC-coupled, 100Ω center-tapped, AC grounded or 100Ω

un-center-tapped, differentially terminated networks.

Copyright © 2007–2013, Texas Instruments Incorporated

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