LMH0056_15 Datasheet, PDF (10/20 Pages) Texas Instruments – HD/SD SDI Reclocker with 4:1 Input Multiplexer

LMH0056
SNLS236C – AUGUST 2006 – REVISED APRIL 2013
Control Inputs and Indicator Outputs
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SERIAL DATA RATE SELECTOR
The Serial Data Rate Selector (RATE [1:0]) permits the user to fix the operating serial data rate. The pins have
internal pull-downs which maintain a logic-low input condition unless externally driven to a logic-high condition.
This input also serves to place the device in a test mode. The codes shown in Table 1 select the desired
operating serial data rate. The LMH0056 then enters either the Auto-Rate Detect mode or a single operating rate.
Selecting the 270 Mbps rate mode may also be used when reclocking DVB-ASI data. DVB-ASI data is MPEG2
coded data that is transmitted in 8B10B coding. The device will reclock this data without harmonic locking.
RATE [1:0]
Code
00
01
10
Table 1. Data Rate Select Input Codes
Data Rate
or Mode
Auto-Rate Detect mode
270 Mbps
1483/1485 Mbps
Comments
143 Mbps rate operation supported only in ARD mode
May be used to support DVB-ASI operation
SERIAL DATA INPUT SELECTOR
The Serial Data Input Selector (SEL [1:0]) allows the user to select the active input channel. Table 2 shows the
input selected for a given state of SEL [1:0].
SEL [1:0] Code
00
01
10
11
Table 2. Data Input Select Codes
Selected Input
SDI0
SDI1
SDI2
SDI3
LOCK DETECT
The Lock Detect (LD) output, when high, indicates that data is being received and the PLL is locked. LD may be
connected to the MUTE input to mute the data and clock outputs when no data signal is being received. See
Table 3.
MUTE
The MUTE input, when low, mutes the serial data and clock outputs. It may be connected to Lock Detect or
externally driven to mute or un-mute the outputs. If MUTE is connected to LD, then the data and clock outputs
are muted when the PLL is not locked. This function overrides the Bypass function: see Table 3. MUTE has an
internal pull-up device to enable the output by default.
BYPASS/AUTO BYPASS
The Bypass/Auto Bypass input, when high, forces the device to output the data without reclocking it. When this
input is low, the device automatically bypasses the reclocking function when the device is in an unlocked
condition or the detected data rate is a rate which the device does not support. See Table 3. BYPASS/AUTO
BYPASS has an internal pull-down device.
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