Datasheet

LMH0384
www.ti.com SNLS308F –APRIL 2009–REVISED APRIL 2013
CARRIER DETECT (CD) AND MUTE
Carrier detect CD indicates if a valid signal is present at the LMH0384 input. If MUTE
REF
is used, the carrier
detect threshold will be altered accordingly. CD provides a high voltage when no signal is present at the
LMH0384 input. CD is low when a valid input signal is detected.
MUTE can be used to manually mute or enable SDO and SDO. Applying a high input to MUTE will mute the
LMH0384 outputs by forcing the output to a logic zero. Applying a low input will force the outputs to be active.
CD and MUTE may be tied together to automatically mute the output when no input signal is present.
AUTO SLEEP
The auto sleep mode allows the LMH0384 to power down when no input signal is detected. If the AUTO SLEEP
pin is set high, the LMH0384 goes into a deep power save mode when no signal is detected. The device powers
on again once an input signal is detected. The auto sleep functionality can be turned off by setting AUTO SLEEP
low or tying this pin to ground. An additional auto sleep setting available in SPI mode can be used to force the
equalizer to power down regardless of whether there is an input signal or not. Auto sleep has precedence over
mute and bypass modes.
In auto sleep mode, the time to power down the equalizer when the input signal is removed is less than 200 µs
and should not have any impact on the system timing requirements. The device will wake up automatically once
an input signal is detected, and the delay between signal detection and full functionality of the equalizer is
negligible (about 1 µs). The overall system will be limited only by the settling time constant of the equalizer
adaptation loop.
INPUT INTERFACING
The LMH0384 accepts either differential or single-ended input. The input must be AC coupled. The Typical
Application (Pin Mode) diagram on the front page shows the typical configuration for a single-ended input. The
unused input must be properly terminated as shown.
The LMH0384 can be optimized for different launch amplitudes via the SPI (see LAUNCH AMPLITUDE
OPTIMIZATION in the SPI REGISTER ACCESS section).
The LMH0384 correctly handles equalizer pathological signals for standard definition and high definition serial
digital video, as described in SMPTE RP 178 and RP 198, respectively.
OUTPUT INTERFACING
SDO and SDO together are internally terminated 100Ω LVDS outputs. These outputs can be DC coupled to most
common differential receivers.
The default output common mode voltage (V
OS
) is 1.25V. The output common mode voltage may be adjusted via
the SPI in 200 mV increments, from 1.05V to 1.85V (see OUTPUT DRIVER ADJUSTMENTS in the SPI
REGISTER ACCESS section). This adjustable output common mode voltage offers flexibility for interfacing to
many types of receivers.
The default differential output swing (V
SSP-P
) is 700 mV
P-P
. The differential output swing may be adjusted via the
SPI in 100 mV increments from 400 mV
P-P
to 800 mV
P-P
(see OUTPUT DRIVER ADJUSTMENTS in the SPI
REGISTER ACCESS section).
The LMH0384 output should be DC coupled to the input of the receiving device as long as the common mode
ranges of both devices are compatible. 100Ω differential transmission lines should be used to connect between
the LMH0384 outputs and the input of the receiving device where possible. Figure 5 shows an example of a DC-
coupled interface between the LMH0384 and LMH0346 SDI reclocker. All that is required is the 100Ω differential
termination as shown. The resistor should be placed as close as possible to the LMH0346 input. If desired, this
network may be terminated with two 50Ω resistors and a center tap capacitor to ground in place of the signal
100Ω resistor.
Figure 6 shows an example of a DC-coupled interface between the LMH0384 and LMH0356 SDI reclocker. The
LMH0356 inputs have 50Ω internal terminations (100Ω differential) to terminate the transmission line, so no
additional components are required.
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