LMH0346 Datasheet, PDF (9/23 Pages) Texas Instruments – HD/SD SDI Reclocker with Dual Differential Outputs

LMH0346
www.ti.com
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 100Ω
differential loads. The differential output level is 750 mV_P-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 (V_EE) 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 50Ω 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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