lmh0346mh National Semiconductor Corporation, lmh0346mh Datasheet - Page 7

• Manufacturer Part Number: lmh0346mh
• Description: 3gbps Hd/sd Sdi Reclocker With Dual Differential Outputs
• Manufacturer: National Semiconductor Corporation

Device Description
The LMH0346 3Gbps 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 ac-
cumulated 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 de-
tect 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 800 mV
or DC-coupled differential loads. Logic inputs and outputs are
LVCMOS compatible.
The device package is a 20-pin e-TSSOP which has an ex-
posed die attach pad. The exposed die attach pad is electri-
cally connected to device ground (V
electrical terminal for the device. This terminal must be con-
nected 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
EE
P-P
FIGURE 1. Equivalent SDI Input Circuit (SDI, SDI)
) and is the negative
±10% into 100Ω AC
7
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 bi-
ased. The input may be AC-coupled if a suitable input bias
voltage is provided. Figure 1 shows the equivalent input circuit
for SDI and SDI.
The LMH0346 has two, retimed, differential, serial data out-
puts, 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 pro-
vide either a second serial data output or a serial clock output.
Figure 2 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 MUTE input is a logic low level. SCO/
SDO2 also mutes when the Bypass mode is activated when
this output is operating as the serial clock output. When mut-
ed, SDO and SDO (or SDO2 and SDO2) will assume opposite
differential output levels. The CML serial data outputs are dif-
ferential 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.
20215008
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