Datasheet
Tx Loopback Mode: Configures the LMH0387 for the output mode with a loopback path (cable driver and
equalizer both enabled). The LMH0387 equalizer is set to auto sleep. If TX_EN is connected to PA0, then PA0 will
drive TX_EN high to enable the LMH0387 cable driver. If this TX_EN Æ PA0 connection is not made, then the
LMH0387 cable driver should be manually enabled by pulling the jumper between TX_EN and GND (TX_EN should
be open). In this mode, the cable driver output on the BNC_IO pin is looped back to the LMH0387 equalizer
outputs (SDO and SDO
¯¯¯¯
), so the cable driver output may be observed both at BNC_IO pin and at the SDO/SDO
¯¯¯¯
output pins.
The Cable Driver TX_EN indicator shows the current status of the TX_EN control (only if TX_EN is connected to
PA0). It is GREEN to indicate TX_EN is driven high and the LMH0387 cable driver is enabled, or OFF to indicate
TX_EN is driven low and the LMH0387 cable driver is disabled.
Equalizer Sleep Mode and Carrier Detect
The Equalizer Sleep Mode control shows the status of the Sleep Mode
register bits and allows control over the sleep mode. The Equalizer Sleep
Mode settings are as follows:
On: Force the equalizer into sleep mode (powered down) regardless of
whether there is an input signal or not.
Off: Disable sleep mode (force equalizer to stay enabled).
Auto: Sleep mode active when no input signal detected (default mode).
The Equalizer Sleep Status indicator shows the current sleep status of the equalizer. It is GREEN to indicate
sleeping or OFF to indicate not sleeping.
The Carrier Detect shows the status of the BNC_IO input carrier detect. It is GREEN to indicate the input signal is
present or OFF to indicate the input signal is absent.
Equalizer Output Swing
The Equalizer Output Swing control shows the current value of the LMH0387 equalizer
output amplitude and allows adjustment in 100 mV increments from 400 mV
P-P
to 800
mV
P-P
. The default setting is 700 mV
P-P
. The Equalizer Output Swing may be set either
by clicking on the “+” or “-” buttons, or by grabbing and spinning the “handle” on the
knob for a quick adjustment.
SD387EVK User Guide 9 of 23
Rev 1.1 © 2010 National Semiconductor Corp.