Datasheet

FIGURE 6. LMH0387 Functional Tab

I/O Mode Control

The I/O Mode Control can be used to control the I/O Mode of the LMH0387,

provided an additional wire is connected between the SD387 TX_EN and the

SPA dongle PA0, as shown in Figure 3. The connection between TX_EN and

PA0 allows software control of the LMH0387 cable driver enable functionality.

If the SD387 TX_EN is not connected to the SPA dongle PA0, then TX_EN

may be controlled manually with a jumper and the I/O Mode Control will have

no effect on the LMH0387 cable driver.

The default LMH0387 I/O Mode setting is the Input (Rx) Mode, or equalizer mode. This default setting allows full

control of the LMH0387 equalizer. The three I/O modes are described below.

Input (Rx) Mode: Configures the LMH0387 for the input mode (equalizer enabled and cable driver disabled). This

is the default setting. The LMH0387 equalizer is set to auto sleep, and if TX_EN is connected to PA0, then PA0 will

drive TX_EN low to disable the LMH0387 cable driver. If this TX_EN Æ PA0 connection is not made, then the

LMH0387 cable driver should be manually disabled by setting a jumper to tie TX_EN to GND.

Output (Tx) Mode: Configures the LMH0387 for the output mode (cable driver enabled and equalizer disabled).

The LMH0387 equalizer is forced to 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).

SD387EVK User Guide 8 of 23