LMH0395 Datasheet, PDF(8/21 Page) Texas Instruments – 3G HD/SD SDI Dual Output Low Power Extended Reach Adaptive Cable Equalizer

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LMH0395 Datasheet, PDF (8/21 Pages) Texas Instruments – 3G HD/SD SDI Dual Output Low Power Extended Reach Adaptive Cable Equalizer

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Block Diagram (Pin Mode)

Device Operation

BLOCK DESCRIPTION

The Equalizer Filter block is a multi-stage adaptive filter. If

Bypass is high, the equalizer filter is disabled.

The DC Restoration / Level Control block receives the dif-

ferential signals from the equalizer filter block. This block

incorporates a self-biasing DC restoration circuit to fully DC

restore the signals. If Bypass is high, this function is disabled.

The signals before and after the DC Restoration / Level Con-

trol block are used to generate the Automatic Equalization

Control (AEC) signal. This control signal sets the gain and

bandwidth of the equalizer filter.

The Carrier Detect block generates the carrier detect signal

based on the SDI input and an adjustment from the Mute

Reference block.

The SPI Control block uses the MOSI, MISO, SCK, and SS

signals in SPI mode to control the SPI registers. SPI_EN se-

lects between SPI mode and pin mode. In pin mode, SPI_EN

is driven logic low.

The Output Drivers produce SDO0, SDO0, SDO1, and

SDO1.

MUTE REFERENCE (MUTEREF)

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 apply-

ing a voltage inversely proportional to the length of cable to

equalize. The applied voltage must be greater than the

MUTEREF floating voltage (typically 1.3V) in order to change

the CD threshold. As the applied MUTEREF voltage is in-

30115702

creased, the amount of cable that can be equalized before

carrier detect is de-asserted and the outputs are muted is de-

creased. MUTEREF may be left unconnected or connected to

ground for normal CD operation. Optionally, the LMH0395 al-

lows the mute reference to be set digitally via SPI register 03h.

Figure 4 shows the minimum MUTEREF input voltage required

to force carrier detect to inactive vs. Belden 1694A cable

length. The results shown are valid for Belden 1694A cable

lengths of 0-200m at 2.97 Gbps, 0-220m at 1.485 Gbps, and

0-400m at 270 Mbps.

2.2

2.0

1.8

1.6

1.4

1.2

0 50 100 150 200 250 300 350 400

BELDEN 1694A CABLE LENGTH (m)

30115712

FIGURE 4. MUTEREF vs. Belden 1694A Cable Length

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