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PDF LMH0024 Data sheet ( Hoja de datos )
| Número de pieza | LMH0024 | |
| Descripción | Adaptive Cable Equalizer | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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PRELIMINARY
February 2006
LMH0024
3.3V SMPTE 259M / 344M Adaptive Cable Equalizer
General Description
The LMH0024 SMPTE 259M / 344M adaptive cable equal-
izer is a monolithic integrated circuit for equalizing data
transmitted over cable (or any media with similar dispersive
loss characteristics). The equalizer operates over a wide
range of data rates from 143 Mbps to 540 Mbps and sup-
ports SMPTE 259M and SMPTE 344M.
The LMH0024 implements DC restoration to correctly handle
pathological data conditions. DC restoration can be by-
passed for low data rate applications. The equalizer is flex-
ible in allowing either single-ended or differential input drive.
Additional features include a mute pin which can be used to
manually mute the output and a cable length indicator which
determines the amount of cable being equalized.
Features
n SMPTE 259M and SMPTE 344M compliant
n Supports DVB-ASI at 270 Mbps
n Data rates: 143 Mbps to 540 Mbps
n Equalizes up to 350 meters of Belden 1694A at 270
Mbps
n Manual bypass, cable length indicator, and output mute
n Single-ended or differential input
n 50Ω differential outputs
n Single 3.3V supply operation
n Industrial temperature range: −40˚C to +85˚C
n 198mW typical power consumption with 3.3V supply
n Footprint compatible with the LMH0034 and the GS9064
Applications
n SMPTE 259M and SMPTE 344M serial digital interfaces
n Serial digital data equalization and reception
n Data recovery equalization
Typical Application
© 2006 National Semiconductor Corporation DS201725
20172501
www.national.com
1 page  
Block Diagram
20172502
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 dis-
abled.
The signals before and after the DC Restoration / Level
Control block are used to generate the Automatic Equal-
ization 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. Cable Length
Indicator (CLI) is derived from this block.
The Output Driver produces SDO and SDO. SDO and SDO
may be force to mute by activating MUTE.
CABLE LENGTH INDICATOR (CLI)
The cable length indicator provides a voltage to indicate the
length of cable being equalized. The CLI voltage decreases
as the cable length increases.
MUTE
MUTE can be used to manually mute or enable the
LMH0024 outputs. MUTE must be tied to a low-level input or
ground for SDO and SDO to be active. Applying a high input
to MUTE will mute the LMH0024 outputs.
INPUT INTERFACING
The LMH0024 accepts either differential or single-ended
input. The input must be AC coupled. Transformer coupling
is not supported.
The LMH0024 correctly handles equalizer pathological sig-
nals for standard definition serial digital video, as described
in SMPTE RP 178.
OUTPUT INTERFACING
The SDO and SDO outputs are internally loaded with 50Ω.
They produce a 750 mVP-P differential output, or a
375 mVP-P single-ended output.
Application Information
PCB LAYOUT RECOMMENDATIONS
Please refer to the following Application Note for the CLC034
on National’s website: AN-1372, “CLC034 PCB Layout
Techniques.” The PCB layout techniques in this application
note apply to the LMH0024 as well.
REPLACING THE GENNUM GS9064
The LMH0024 is footprint compatible with the Gennum
GS9064. Pin 16 (MUTE) of the LMH0024 must be connect to
ground for correct operation.
SUPPLY CURRENT VS. CABLE LENGTH
The supply current (ICC) depends on the amount of cable
being equalized. The current is highest for short cable and
decreases as the cable length is increased. Figure 1 shows
supply current vs. Belden 1694A cable length for 270 Mbps
data.
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| Páginas | Total 7 Páginas | |
| PDF Descargar | [ Datasheet LMH0024.PDF ] | |
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