The design procedure for cable equalizer
with loop-through applications is as follows:
- Select a power supply that meets the DC
and AC requirements in Recommended Operating Conditions.
- Choose small 0402 surface mount ceramic
capacitors for AC-coupling capacitors to maintain characteristic impedance.
- Choose a high-quality, 75Ω BNC connector
that is capable of supporting 11.88Gbps applications. Consult a BNC supplier regarding
insertion loss, impedance specifications, and recommended footprint for meeting SMPTE
return loss.
- Follow detailed high-speed layout
recommendations provided in Layout Guidelines to ensure optimal signal quality when interconnecting 75Ω and 100Ω signals to the
LMH12x9.
- Determine whether SPI or SMBus
communication is necessary. If the LMH12x9 must be programmed with
settings other than what is offered by pin control, users must use SPI or SMBus mode for
additional programming.
- Configure all two-level and four-level
pins according to the desired use case. Note that pin settings can be overridden by
register control.
- Tune the VOD_DE 100Ω driver control pin
to equalize the PCB output trace following OUT0± and OUT1± (if used). Use register control
for more tuning options if necessary.
- If SDI_OUT is used for diagnostic or
cascade applications, tune the SDI_VOD output amplitude control pin for optimal signal
quality depending on the cable length attached at SDI_OUT+. Use register control for more
tuning options if necessary.