LMH0074 Datasheet, PDF (5/14 Pages) Intersil Corporation – SMPTE 259M / 344M Adaptive Cable Equalizer

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Block Diagram
SDI
SDI
Equalizer
Filter
DC
Restoration/
Level Control
LMH0074
SNLS277D – AUGUST 2007 – REVISED APRIL 2013
Output
Driver
BYPASS
SDO
SDO
Energy
Detect
Energy
Detect
6
Automatic
Equalization
Control
Carrier
Detect/
Mute
CD
MUTE
MUTE_REF
AEC+ AEC-
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 differential 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 Control block are used to generate the Automatic
Equalization Control (AEC) signal. This control signal sets the gain and bandwidth of the equalizer filter. The
loop response in the AEC block is controlled by an external 1µF capacitor placed across the AEC+ and AEC-
pins.
The Carrier Detect / Mute block generates the carrier detect signal and controls the mute function of the output.
This block utilizes the CD and MUTE signals along with Mute Reference (MUTE_REF).
The Output Driver produces SDO and SDO.
MUTE REFERENCE (MUTE_REF)
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
length of cable to equalize. As the applied MUTE_REF voltage is increased, the amount of cable that can be
equalized before carrier detect is de-asserted and the outputs are muted is decreased. MUTE_REF may be left
unconnected for maximum equalization before muting.
CARRIER DETECT (CD) AND MUTE
Carrier detect CD indicates if a valid signal is present at the LMH0074 input. If MUTE_REF is used, the carrier
detect threshold will be altered accordingly. CD provides a high voltage when no signal is present at the
LMH0074 input. CD is low when a valid input signal is detected.
MUTE can be used to manually mute or enable SDO and SDO. Applying a high input to MUTE will mute the
LMH0074 outputs. Applying a low input will force the outputs to be active.
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: LMH0074
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