Datasheet

Equalizer Input Launch Level Control
Note: The GUI automatically sets the nominal equalizer launch amplitude setting upon
startup (specifically, it writes 30h to SPI register 02h). This nominal setting is required
for correct equalizer operation with the default SMPTE 800 mV
P-P
launch amplitude
and no external attenuation. If the equalizer launch amplitude setting is changed, it
can be instantly set back to this nominal setting by clicking the “Set To Default” button.
The Equalizer Input Launch Level Control is useful to compensate for attenuation of
the input signal prior to the equalizer due to a passive splitter or non-ideal input
termination network.
The Coarse Amplitude control shows the current setting of the Coarse Control register
and may be used to set the input for either 0 dB (default) or 6 dB of input attenuation.
At the default setting of 0 dB, the equalizer operates normally and expects a launch
amplitude of 800 mV
P-P
. With the Coarse Amplitude set to -6 dB, the equalizer is
optimized for input signals with 6 dB of input attenuation (400 mV
P-P
).
The Launch Amplitude Fine Tuning may be used to further fine tune the equalizer
input compensation, from -0.2 dB to 4.1 dB. The Launch Amplitude Fine Tuning may
be set either by clicking on the “+” or “-” buttons, or by grabbing and spinning the
“handle” on the knob for a quick adjustment.
Equalizer Cable Length
The Equalizer Cable Length shows the interpreted Belden 1694A cable length of the CLI
register, both with a visual bar graph and a decimal readout. The Equalizer Cable Length is
only valid when an input signal is detected, and is greyed out when there is no input to the
LMH0387 equalizer.
SD387EVK User Guide 11 of 23
Rev 1.1 © 2010 National Semiconductor Corp.