LMH0056_07 Datasheet, PDF(10/16 Page) National Semiconductor (TI) – HD/SD SDI Reclocker with 4:1 Input Multiplexer

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LMH0056_07 Datasheet, PDF (10/16 Pages) National Semiconductor (TI) – HD/SD SDI Reclocker with 4:1 Input Multiplexer

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20201909

FIGURE 2. Equivalent SDO Output Circuit (SDO, SDO, SCO/SDO2, SCO/SDO2)

OPERATING SERIAL DATA RATES

This device operates at serial data rates of 143 Mbps, 270

Mbps, 1483 Mbps and 1485 Mbps. The device does not lock

to harmonics of these rates. The device does not lock and

automatically enters the reclocker bypass mode for the fol-

lowing data rates: 177 Mbps, 360 Mbps, and 540 Mbps.

SERIAL DATA CLOCK/SERIAL DATA 2 OUTPUT

The Serial Data Clock/Serial Data 2 Output is controlled by

the SCO_EN input and provides either a second retimed se-

rial data output or a low jitter differential clock output appro-

priate to the serial data rate being processed. When operating

as a serial clock output, the rising edge of the clock will be

positioned within the corresponding serial data bit interval

within 10% of the center of the data interval.

Differential output SCO/SDO2 functions as the second serial

data output when the SCO_EN input is a logic-low level. This

output functions as the serial data-rate clock output when the

SCO_EN input is a logic-high level. The SCO_EN input has

an internal pull-down device and the default state of SCO_EN

is low (serial data output 2 enabled). SCO/SDO2 is muted

when the MUTE input is a logic low level. When the Bypass

mode is activated and this output is functioning as a serial

clock output, the output will also be muted.

Control Inputs and Indicator

Outputs

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 ex-

ternally 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 op-

erating 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.

TABLE 1. Data Rate Select Input Codes

RATE [1:0] Data Rate

Code

or Mode

Comments

Auto-Rate 143 Mbps rate operation

Detect

supported only in ARD mode

mode

270 Mbps May be used to support DVB-

ASI operation

1483/1485

Mbps

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