NSC LMH0044SQ

LMH0044
SMPTE 292M / 259M Adaptive Cable Equalizer
General Description
Features
The LMH0044 SMPTE 292M / 259M adaptive cable equalizer
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 1.485 Gbps and supports
SMPTE 292M, SMPTE 344M and SMPTE 259M.
The LMH0044 implements DC restoration to correctly handle
pathological data conditions (DC restoration may be bypassed for low data rate applications). The equalizer may be
driven in either a single ended or differential configuration.
Additional features include separate carrier detect and output
mute pins which may be tied together to mute the output when
no signal is present. A programmable mute reference is provided to mute the output at a selectable level of signal degradation.
■ SMPTE 292M, SMPTE 344M and SMPTE 259M
compliant
■ Supports DVB-ASI at 270 Mbps
■ High data rates: 143 Mbps to 1.485 Gbps
■ Equalizes up to 200 meters of Belden 1694A at 1.485
Gbps or up to 400 meters of Belden 1694A at 270 Mbps
■ Manual bypass and output mute with a programmable
■
■
■
■
■
threshold
Single-ended or differential input
50Ω differential outputs
Single 3.3V supply operation
208mW typical power consumption with 3.3V supply
Replaces the GS1574 and GS1574A
Applications
■ SMPTE 292M, SMPTE 344M, and SMPTE 259M serial
digital interfaces
■ Serial digital data equalization and reception
■ Data recovery equalization
Typical Application
20177001
© 2007 National Semiconductor Corporation
201770
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LMH0044 SMPTE 292M / 259M Adaptive Cable Equalizer
June 2007
LMH0044
Absolute Maximum Ratings (Note 1)
Supply Voltage
Input Voltage (all inputs)
Storage Temperature Range
Junction Temperature
Lead Temperature
(Soldering 4 Sec)
Package Thermal Resistance
θJA 16-pin LLP
θJC 16-pin LLP
ESD Rating (HBM)
ESD Rating (MM)
Recommended Operating
Conditions
−0.5V to 3.6V
−0.3V to VCC+0.3V
−65°C to +150°C
+150°C
Supply Voltage (VCC – VEE)
Input Coupling Capacitance
AEC Capacitor (Connected between
AEC+ and AEC-)
Operating Free Air Temperature (TA)
+260°C
3.3V ±5%
1.0 µF
1.0 µF
0°C to +85°C
+43°C/W
+9°C/W
8kV
250V
DC Electrical Characteristics
Over Supply Voltage and Operating Temperature ranges, unless otherwise specified (Notes 2, 3).
Symbol Parameter
VCMIN
Input Common Mode Voltage
VSDI
Input Voltage Swing
VCMOUT
Output Common Mode Voltage
VSDO
Output Voltage Swing
Conditions
Reference
Min
SDI, SDI
At LMH0044 input, (Notes 4, 6)
720
50Ω load, differential
MUTEREF
MUTEREF Range
CD Output Voltage
Carrier not present
CD
2.6
MUTE
3.0
800
Supply Current
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950
(Note 7)
750
mVP-P
1.3
V
0.7
V
V
V
V
63
2
mVP−P
V
Max to force outputs active
ICC
V
0.4
Min to mute outputs
Units
VCC –
VSDO/2
Carrier present
MUTE Input Voltage
Max
1.9
SDO, SDO
MUTEREF DC Voltage (floating)
Typ
0.8
V
77
mA
LMH0044
AC Electrical Characteristics
Over Supply Voltage and Operating Temperature ranges, unless otherwise specified (Note 3).
Symbol Parameter
BRSDI
Jitter for various Cable Lengths
(with equalizer pathological)
tr,tf
Conditions
Input Data Rate
Reference
Min
SDI, SDI
143
Typ
Max
Units
1485
Mbps
270 Mbps, Belden 1694A,
400 meters (Note 4)
0.2
UI
270 Mbps, Belden 8281,
280 meters (Note 4)
0.2
UI
1.485 Gbps, Belden 1694A,
140 meters (Note 4)
0.25
UI
1.485 Gbps, Belden 8281,
100 meters (Note 4)
0.25
UI
1.485 Gbps, Belden 1694A,
200 meters (Note 4)
0.3
UI
Output Rise Time, Fall Time
20% – 80%, (Note 4)
Mismatch in Rise/Fall Time
(Note 4)
tOS
Output Overshoot
ROUT
SDO, SDO
100
220
ps
2
15
ps
(Note 4)
1
5
%
Output Resistance
single-ended, (Note 5)
50
RLIN
Input Return Loss
(Note 8)
RIN
Input Resistance
single-ended
CIN
Input Capacitance
single-ended, (Note 5)
SDI, SDI
15
Ω
18-20
dB
1.3
kΩ
1
pF
Note 1: "Absolute Maximum Ratings" are those parameter values beyond which the life and operation of the device cannot be guaranteed. The stating herein of
these maximums shall not be construed to imply that the device can or should be operated at or beyond these values. The table of "Electrical Characteristics"
specifies acceptable device operating conditions.
Note 2: Current flow into device pins is defined as positive. Current flow out of device pins is defined as negative. All voltages are stated referenced to VEE = 0
Volts.
Note 3: Typical values are stated for VCC = +3.3V and TA = +25°C.
Note 4: Specification is guaranteed by characterization.
Note 5: Specification is guaranteed by design.
Note 6: The maximum input voltage swing assumes a nonstressing, DC-balance signal; specifically, the SMPTE-recommended color bar test signal. Pathological
or other stressing signals may not be used. This specification is for 0m cable only.
Note 7: Supply current depends on the amount of cable being equalized. The current is highest for short cable and decreases as the cable length is increased.
Refer to Figures 1, 2.
Note 8: Input return loss is dependent on board design. The LMH0044 meets this specification on the SD044 evaluation board from 5MHz to 1.5GHz.
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LMH0044
Connection Diagram
20177003
16-Pin LLP
Order Number LMH0044SQ
See NS Package Number SQB16A
Pin Descriptions
Pin #
Name
Description
1
VEE
Negative power supply (ground).
2
SDI
Serial data true input.
3
SDI
Serial data complement input.
4
VEE
Negative power supply (ground).
5
AEC+
AEC loop filter external capacitor (1µF) positive connection.
6
AEC-
AEC loop filter external capacitor (1µF) negative connection.
7
BYPASS
Bypasses equalization and DC restoration when high. No equalization occurs in this mode.
8
MUTEREF
Mute reference. Sets the threshold for CD and (with CD tied to MUTE) determines the maximum
cable to be equalized before muting. MUTEREF may be unconnected for maximum equalization.
9
VEE
Negative power supply (ground).
10
SDO
Serial data complement output.
11
SDO
Serial data true output.
12
VEE
Negative power supply (ground).
13
VCC
Positive power supply (+3.3V).
14
MUTE
Output mute. To disable the mute function and enable the output, MUTE must be tied to GND or
a low level signal. To force the outputs to a muted state, tie to VCC. CD may be tied to this pin to
inhibit the output when no input signal is present. MUTE has no function in BYPASS mode.
15
CD
Carrier detect. CD is high when no signal is present. CD has no function in BYPASS mode.
16
VCC
Positive power supply (+3.3V).
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LMH0044
Block Diagram
20177002
CARRIER DETECT (CD) AND MUTE
Carrier detect CD indicates if a valid signal is present at the
LMH0044 input. If MUTEREF is used, the carrier detect threshold will be altered accordingly. CD provides a high voltage
when no signal is present at the LMH0044 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 LMH0044
outputs. Applying a low input will force the outputs to be active.
CD and MUTE may be tied together to automatically mute the
output when no input signal is present.
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
(MUTEREF).
The Output Driver produces SDO and SDO.
INPUT INTERFACING
The LMH0044 accepts either differential or single-ended input. The input must be AC coupled. Transformer coupling is
not supported.
The LMH0044 correctly handles equalizer pathological signals for standard definition and high definition serial digital
video, as described in SMPTE RP 178 and RP 198, respectively.
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 applying a voltage inversely proportional to the length of cable to
equalize. As the applied MUTEREF voltage is increased, the
amount of cable that can be equalized before carrier detect is
de-asserted and the outputs are muted is decreased.
MUTEREF may be left unconnected for maximum equalization
before muting.
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.
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LMH0044
Application Information
PCB LAYOUT RECOMMENDATIONS
Please refer to the following Application Note on National's
website: AN-1372, “LMH0034 PCB Layout Techniques.”
The PCB layout techniques in the application note apply to
the LMH0044 as well.
REPLACING THE GENNUM GS1574A
The LMH0044 is footprint compatible with the Gennum
GS1574A.
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 1.485 Gbps
data and Figure 2 shows supply current vs. Belden 1694A
cable length for 270 Mbps data.
20177015
FIGURE 2. Supply Current vs. Belden 1694A Cable
Length, 270 Mbps
20177013
FIGURE 1. Supply Current vs. Belden 1694A Cable
Length, 1.485 Gbps
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LMH0044
Physical Dimensions inches (millimeters) unless otherwise noted
16-Pin LLP
Order Number LMH0044SQ
NS Package Number SQB16A
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LMH0044 SMPTE 292M / 259M Adaptive Cable Equalizer
Notes
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Copyright© 2007 National Semiconductor Corporation
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