Datasheet

SP
t
BUF
t
HD:STA
t
LOW
t
R
t
HD:DAT
t
HIGH
t
F
t
SU:DAT
ST
SP
t
SU:STO
SCL
SDA
ST
t
SU:STA
LMH0307
www.ti.com SNLS286I –APRIL 2008–REVISED APRIL 2013
TIMING DIAGRAM
Figure 3. SMBus Timing Parameters
DEVICE OPERATION
INPUT INTERFACING
The LMH0307 accepts either differential or single-ended input. For single-ended operation, the unused input
must be properly terminated.
OUTPUT INTERFACING
The LMH0307 uses current mode outputs. Single-ended output levels are 800 mV
P-P
into 75Ω AC-coupled
coaxial cable with an R
REF
resistor of 750Ω. The R
REF
resistor is connected between the R
REF
pin and V
CC
. The
only resistor value that should be used for R
REF
is 750Ω.
The R
REF
resistor should be placed as close as possible to the R
REF
pin. In addition, the copper in the plane
layers below the R
REF
network should be removed to minimize parasitic capacitance.
OUTPUT SLEW RATE CONTROL
The LMH0307 output rise and fall times are selectable for either SMPTE 259M or SMPTE 424M / 292M
compliance via the SD/HD pin. For slower rise and fall times, or SMPTE 259M compliance, SD/HD is set high.
For faster rise and fall times, or SMPTE 424M and SMPTE 292M compliance, SD/HD is set low. SD/HD may
also be controlled using the SMBus, provided the SD/HD pin is held low. SD/HD has an internal pulldown.
OUTPUT ENABLE
The SDO0/SDO0 and SDO1/SDO1output drivers can be enabled or disabled with the ENABLE pin. When set
low, both output drivers are powered off and the LMH0307 enters a deep power save mode. ENABLE has an
internal pullup.
INPUT LOSS OF SIGNAL DETECTION (LOS)
The LMH0307 detects when the input signal does not have a video-like pattern. Self oscillation and low levels of
noise are rejected. This loss of signal detect allows a very sensitive input stage that is robust against coupled
noise without any degradation of jitter performance.
Via the SMBus, the loss of signal detect can either add an input offset or mute the outputs. An offset is added by
default. Additionally, the loss of signal detect can be linked to the ENABLE functionality so that when the LOS
goes low, ENABLE will also go low.
OUTPUT CABLE DETECTION
The LMH0307 detects when an output is locally terminated. When a video signal (or AC test signal) is present on
SDI, the device senses the SDO and SDO amplitudes. If the output is not properly terminated (via a terminated
cable or local termination), the amplitude will be higher than expected, and the Termination Fault signal is
asserted. The Termination Fault signal is de-asserted when the proper termination is applied. This feature allows
the system designer the flexibility to react to cable attachment and removal. Note that a long length of cable will
look like a proper termination at the device output.
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Product Folder Links: LMH0307