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LMH0346 Datasheet, PDF (12/23 Pages) Texas Instruments – HD/SD SDI Reclocker with Dual Differential Outputs
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LMH0346
SNLS248J – APRIL 2007 – REVISED APRIL 2013
www.ti.com
SD/HD
The SD/HD output indicates whether the LMH0346 is processing SD or HD / 3 Gbps data rates. It may be used
to control another device such as the LMH0302 cable driver. When this output is high it indicates that the data
rate is 270 Mbps. When low, the indicated data rate is 1483, 1485, 2967, or 2970 Mbps. The SD/HD output is a
registered function and is only valid when the PLL is locked and the Lock Detect output is high. When the PLL is
not locked (the Lock Detect output is low), the SD/HD output defaults to HD (low). The SD/HD output is
undefined for a short time after lock detect assertion or deassertion due to a data rate change on SDI. See
Figure 5 for a timing diagram showing the relationship between SDI, Lock Detect, and SD/HD.
SDI
NO DATA
270 MBPS DATA
NO DATA
1485 MBPS DATA
NO DATA
TACQ
T2
TACQ
T2
Lock
Detect
T1
T1
T1
SD/HD
SDI
NO DATA
270 MBPS DATA
TACQ
1485 MBPS DATA
2970 MBPS DATA
270 MBPS DATA
TACQ
TACQ
TACQ
T2
T2
T2
Lock
Detect
SD/HD
T1
T1
T1
T1
T1
TACQ = Acquisition Time, defined in the AC Electrical Characteristics Table
T1 = Time from Lock Detect assertion or deassertion until SD/HD output is valid, typically 37 ns (one 27 MHz clock period)
T2 = Time from SDI input change until Lock Detect de-assertion, 1 ms maximum. SD/HD output is not valid during this time.
Figure 5. SDI, Lock Detect, and SD/HD Timing
SCO_EN
Input SCO_EN enables the SCO/SDO2 differential output to function either as a serial clock or second serial
data output. SCO/SDO2 functions as a serial clock when SCO_EN is high. This pin has an internal pull-down
device. The default state (low) enables the SCO/SDO2 output as a second serial data output.
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