LMH0384 Datasheet, PDF (18/29 Pages) National Semiconductor (TI) – 3 Gbps HD/SD SDI Extended Reach and Configurable Adaptive Cable Equalizer

LMH0384
SNLS308G – APRIL 2009 – REVISED JUNE 2015
8 Application and Implementation
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NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The LMH0384 is a single-channel, 3-Gbps HD - SD SDI Adaptive Cable Equalizer designed to equalize data
transmitted over cable or any media with similar dispersive loss characteristics. The equalizer operates over a
wide range of data rates from 125 Mbps to 2.97 Gbps and supports ST 424, ST 292, ST 344, and ST 259.
Additional features include separate carrier detect and output mute pins which may be tied together to mute the
output when no signal is present. A programmable mute reference is provided to mute the output at a selectable
level of signal degradation. The bypass pin allows the adaptive equalizer to be bypassed. The LMH0384 accepts
either a differential or single-ended input. The input must be AC-coupled.
The LMH0384 correctly handles equalizer pathological signals for standard definition and high definition serial
digital video, as described in ST RP 178 and RP 198, respectively.
8.1.1 Replacing the LMH0344
In pin mode, the LMH0384 is a drop-in replacement for the LMH0344SQ SDI cable equalizer. When replacing an
LMH0344 with an LMH0384, it is important to consider the following points:
1. The LMH0384 auto sleep function is mapped to pin 12 which is a ground pin on the LMH0344SQ. When this
pin is grounded on the LMH0384, the auto sleep function is disabled. To enable auto sleep mode on the
LMH0384, pin 12 must be pulled high.
2. Pin 4 and pin 9 on the LMH0344SQ are true ground pins. For the LMH0384, pin 4 and pin 9 may be driven
logic low in pin mode (they do not require a true ground connection).
3. The LMH0384 has lower input capacitance than the LMH0344 which allows for improved input return loss.
The input return loss network may need to be modified. In most cases, the LMH0384 should provide superior
input return loss.
4. The LMH0384 default output common-mode voltage is different than that of the LMH0344. In most cases,
this should not cause an issue. The LMH0384 and LMH0344 outputs can both be DC coupled to TI's SDI
reclockers and cable drivers. In addition, the LMH0384 output can be DC coupled to LVDS and other inputs
that require lower input common-mode voltages than the LMH0344. The LMH0384 output common-mode
voltage is adjustable through the SPI.
8.2 Typical Application
Figure 11 and Figure 12 show the application circuit for the LMH0384 in SPI mode and Pin mode.
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