LMH0356_08 Datasheet, PDF (8/16 Pages) National Semiconductor (TI) – 3 Gbps HD/SD SDI Reclocker with 4:1 Input Mux and FR4 EQs

Device Description
The LMH0356 3 Gbps HD/SD SDI Reclocker with 4:1 Input
Mux and FR4 EQs is used in many types of digital video signal
processing equipment. Supported serial digital video stan-
dards 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 LMH0356 retimes
the serial data stream to suppress accumulated jitter. It pro-
vides two low-jitter, differential, serial data outputs. The sec-
ond 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/man-
ual 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 LVC-
MOS compatible.
The device package is a 48–pin LLP with an exposed die at-
tach pad. The exposed die attach pad is electrically connect-
ed to device ground (V_EE) and is the primary electrical terminal
for the device. This terminal must be connected to the nega-
tive power supply or circuit ground.
Serial Data Inputs, Serial Data and
Clock Outputs
SERIAL DATA INPUT AND OUTPUTS
The differential serial data inputs, SDI0-SDI3, accept serial
digital video data at the rates specified in Table 1. Figure 1
shows the equivalent input circuit for SDI[3:0] and SDI[3:0].
The serial data inputs are differential LVPECL compatible.
These inputs have 50Ω internal terminations (100Ω differen-
tial) with an internal bias as shown in Figure 1. These inputs
are intended to be DC coupled to devices such as the
LMH0344 adaptive cable equalizer. DC-coupled inputs must
be kept within the specified common mode range. The inputs
may be AC coupled if the input signal is outside the
LMH0356's input common mode range (such as when inter-
facing to 5V PECL), and in that case the bias is supplied
internally so no additional input biasing is required. See Ap-
plication Information for more information on input interfacing.
The LMH0356 provides four independent, equalized and mul-
tiplexed data inputs. The active input channel is selected via
the SEL0 and SEL1 pins, as shown in Table 2. The equalizer
on each of the four inputs is capable of equalizing up to 30”
of FR4 trace without the need for programming for different
trace lengths or data rates.
The LMH0356 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 or the LMH0031 deserializer. Output SCO/SDO2
is multiplexed and can provide 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 OUTPUT 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
muted, SDO and SDO (or SDO2 and SDO2) will assume op-
posite differential output levels. The CML serial data outputs
are differential LVPECL compatible. These outputs have in-
ternal 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.
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FIGURE 1. Equivalent SDI Input Circuit (SDI[3:0], SDI[3:0])
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