0

50 100 150 200 250 300 350 400

1.2

1.4

1.6

1.8

2.0

2.2

BELDEN 1694A CABLE LENGTH (m)

LMH0395

SNLS323M – AUGUST 2010 – REVISED JULY 2015

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Feature Description (continued)

The SPI Control block uses the MOSI, MISO, SCK, and SS signals in SPI mode to control the SPI registers.

SPI_EN selects between SPI mode and pin mode. In pin mode, SPI_EN is driven logic low.

The Output Drivers produce SDO0, SDO0, SDO1, and SDO1.

The mute reference sets the threshold for CD and (with CD tied to MUTE) determines the amount of cable to

equalize before automatically muting the outputs. This is set by applying a voltage inversely proportional to the

left unconnected or connected to ground for normal CD operation. Optionally, the LMH0395 allows the mute

reference to be set digitally through SPI register 03h.

cable length. The results shown are valid for Belden 1694A cable lengths of 0-200 m at 2.97 Gbps, 0-220 m at

1.485 Gbps, and 0-400 m at 270 Mbps.

7.3.2 Carrier Detect (CD) and Mute

Carrier detect CD indicates if a valid signal is present at the LMH0395 input. This signal is a logical OR operation

high voltage when no signal is present at the LMH0395 input. CD is low when a valid input signal is detected.

MUTE can be used to manually mute or enable the output drivers. Applying a high input to MUTE will mute the

LMH0395 outputs by forcing the output to a logic 1. Applying a low input will force the outputs to be active.

In pin mode, CD and MUTE may be tied together to automatically mute the output when no input signal is

present.

7.3.3 Input Interfacing

The LMH0395 accepts single-ended input. The input must be AC coupled. The Functional Block Diagram

diagram shows the typical configuration for a single-ended input. The unused input must be properly terminated

as shown in Figure 7 or Figure 8.

The LMH0395 can be optimized for different launch amplitudes through the SPI (see Launch Amplitude

Optimization in the SPI Register Access section).

The LMH0395 correctly handles equalizer pathological signals for standard definition and high definition serial

digital video, as described in ST RP 178 and RP 198, respectively.

12

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