LMH0395SQX/NOPB National Semiconductor, LMH0395SQX/NOPB Datasheet - Page 8

• Manufacturer Part Number: LMH0395SQX/NOPB
• Description: IC EQUALIZER DUAL CABLE 24-LLP
• Manufacturer: National Semiconductor

Specifications of LMH0395SQX/NOPB

• Applications: Amplifier
• Interface: SPI Serial
• Voltage - Supply: 2.5V
• Package / Case: *
• Mounting Type: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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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 (MUTE
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
MUTE
the CD threshold. As the applied MUTE
REF
floating voltage (typically 1.3V) in order to change
REF
)
REF
voltage is in-
8
creased, the amount of cable that can be equalized before
carrier detect is de-asserted and the outputs are muted is de-
creased. MUTE
ground for normal CD operation. Optionally, the LMH0395 al-
lows the mute reference to be set digitally via SPI register 03h.
Figure 4
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.
FIGURE 4. MUTE
shows the minimum MUTE
2.2
2.0
1.8
1.6
1.4
1.2
0
REF
BELDEN 1694A CABLE LENGTH (m)
50 100 150 200 250 300 350 400
may be left unconnected or connected to
REF
vs. Belden 1694A Cable Length
REF
input voltage required
30115702
30115712