LM4731
Stereo 25W Audio Power Amplifier with Mute and
Standby Modes
General Description
The LM4731 is a stereo audio amplifier capable of delivering
typically 25W per channel of continuous average output
power into a 4
or 8 load with less than 10% THD+N from
20Hz - 20kHz.
Each amplifier has an independent smooth transition fade-
in/out mute and a power conserving standby mode which
can be controlled by external logic.
The LM4731 has short circuit protection and a thermal shut
down feature that is activated when the die temperature
exceeds 150C. The LM4731 also has a under voltage lock
out feature for click and pop free power off and on.
The LM4731 has a wide operating supply range from +/-10V
- +/-28V allowing for lower cost unregulated power supplies
to be used.
Key Specifications
j
Output Power into 4
or 8, 10% THD+N 25W (typ)
j
THD+N at 1kHz with 2 x 1W into 8
0.02% (typ)
j
Mute Attenuation
85dB (typ)
j
PSRR with f
RIPPLE
= 120Hz,
V
RIPPLE
= 1V
RMS
50dB (typ)
j
Slew Rate
18V/s (typ)
j
Standby Current (+/-22V)
4.8mA (typ)
Features
n
Minimal amount of external components necessary
n
Quiet fade-in/out mute mode
n
Low current Standby-mode
Applications
n
Audio amplifier for high-end stereo TVs
n
Audio amplifier for component stereo
n
Audio amplifier for compact stereo
n
Audio amplifier for PC satellite speaker systems
n
Audio amplifier for self powered speakers
Connection Diagrams
Plastic Package
TO-220 Top Marking (Note 12)
20060352
Top View
Non-Isolated Package
Order Number LM4731TA
See NS Package Number TA15A
20060375
Top View
U - Wafer Fab Code
Z - Assembly Plant Code
XY - Date Code
TT - Die Traceability
LM4731TA - LM4731TA
July 2003
LM4731
Stereo
25W
Audio
Power
Amplifier
with
Mute
and
Standby
Modes
2003 National Semiconductor Corporation
DS200603
www.national.com
Absolute Maximum Ratings
(Notes 1,
2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage |V
+
| + |V
-
|
56V
Common Mode Input Voltage
V
+
or V
-
Differential Input Voltage
56V
Output Current
Internally Limited
Power Dissipation (Note 3)
50W
ESD Susceptability (Note 4)
2.0kV
ESD Susceptability (Note 6)
250V
Junction Temperature (T
JMAX
) (Note 9)
150C
Soldering Information
T Package (10 sec.)
260C
Storage Temperature
-40C to +150C
Thermal Resistance
JA
(TA)
43C/W
JC
(TA)
1.5C/W
Operating Ratings
(Notes 1, 2)
Temperature Range
T
MIN
T
A
T
MAX
-20C
T
A
+85C
Supply Voltage |V
+
| + |V
-
|
20V
V
TOTAL
56V
Electrical Characteristics
(Notes 1, 2)
The following specifications apply for V
+
= +22V, V
-
= -22V and R
L
= 8
unless otherwise specified. Limits apply for T
A
=
25C.
Symbol
Parameter
Conditions
LM4731
Units
(Limits)
Typical
Limit
(Note 6)
(Notes 7, 8)
|V
+
| + |V
-
|
Power Supply Voltage (Note 10)
GND - V
-
9V
20
56
V (min)
V (max)
A
M
Mute Attenuation
85
dB
P
O
Output Power (RMS)
THD+N = 10% (max), f = 1kHz
|V
+
| = |V
-
| = 18V, R
L
= 4
|V
+
| = |V
-
| = 22V, R
L
= 8
25
25
20
22
W (min)
W (min)
THD+N = 1% (max), f = 1kHz
|V
+
| = |V
-
| =18V, R
L
= 4
|V
+
| = |V
-
| = 22V, R
L
= 8
20
20
18
18
W (min)
W (min)
THD+N
Total Harmonic Distortion +
Noise
P
O
= 1W, f = 1kHz
A
V
= 26dB,
|V
+
| = |V
-
| = 18V, R
L
= 4
|V
+
| = |V
-
| = 22V, R
L
= 8
0.03
0.02
0.5
0.3
% (max)
% (max)
X
talk
Channel Separation
P
O
= 10W
f = 1kHz
f = 10kHz
65
60
dB
dB
SR
Slew Rate (Note 11)
V
IN
= 2.0V
p-p
, t
rise
= 2ns
18
V/s
I
DD
Total Quiescent Power Supply
Current
V
CM
= 0V, V
O
= 0V, I
O
= 0A
Standby off (Play Mode)
Standby on (Standby Mode)
95
4.8
110
6
mA (max)
mA (max)
V
OS
Input Offset Voltage
V
CM
= 0V, I
O
= 0 mA
2.0
15
mV (max)
I
B
Input Bias Current
V
CM
= 0V, I
O
= 0 mA
0.2
A
PSRR
Power Supply Rejection Ratio
V
RIPPLE
= 1V
RMS
, f
RIPPLE
= 120Hz sine
wave
Inputs terminated to GND
50
dB
A
VOL
Open Loop Voltage Gain
R
L
= 2 k
, V
O
= 20V
110
dB
e
IN
Input Noise
IHF -- A-Weighting Filter
2.0
8
V (max)
R
IN
= 600
(Input Referred)
Standby
V
IL
Standby Low Input Voltage
Not in Standby Mode (Play)
0.8
V (max)
V
IH
Standby High Input Voltage
In Standby Mode
2.0
2.5
V (min)
Mute
LM4731
www.national.com
3
Electrical Characteristics
(Notes 1, 2) (Continued)
The following specifications apply for V
+
= +22V, V
-
= -22V and R
L
= 8
unless otherwise specified. Limits apply for T
A
=
25C.
Symbol
Parameter
Conditions
LM4731
Units
(Limits)
Typical
Limit
(Note 6)
(Notes 7, 8)
V
IL
Mute Low Input Voltage
Not in Mute Mode (Play)
0.8
V (max)
V
IH
Mute High Input Voltage
In Mute Mode
2.0
2.5
V (min)
Note 1: All voltages are measured with respect to the ground pin, unless otherwise specified.
Note 2: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
functional, but do not guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which
guarantee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limit
is given. However, the typical value is a good indication of a device's performance.
Note 3: The maximum power dissipation must be de-rated at elevated temperatures and is dictated by T
JMAX
,
JC
, and the ambient temperature T
A
. The maximum
allowable power dissipation is P
DMAX
= (T
JMAX
-T
A
) /
JC
or the number given in the Absolute Maximum Ratings, whichever is lower. For the LM4731, T
JMAX
= 150C
and the typical
JC
is 1.5C/W for the TA15A package . Refer to the Thermal Considerations section for more information.
Note 4: Human body model, 100 pF discharged through a 1.5 k
resistor.
Note 5: Machine Model: a 220pF - 240pF discharged through all pins.
Note 6: Typical specifications are sepcified at 25C and represent the parametric norm.
Note 7: Tested limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
Note 8: Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis.
Note 9: The operating junction temperature maximum is 150C. However, the instantaneous Safe Operating Area temperature is 250C.
Note 10: V
-
must have at least -9V at its pin with reference to GND in order for the under-voltage protection circuitry to be disabled. In addition, the voltage
differential between V
+
and V
-
must be greater than 14V.
Note 11: The feedback compensation network limits the bandwidth of the closed-loop response causing the skew rate to be reduced by the high frequency roll-off.
Without feedback compensation the slew rate is typically larger.
Note 12: The LM4731TA package TA15A is a non-isolated package setting the tab of the device and the heat sink to V-potential when the LM4731TA is directly
mounted to the heat sink using only thermal compound. If a mica washer is used in addition to thermal compound,
CS
(case to sink) is increased, but the heat sink
will be electrically isolated from V-.
Bridged Amplifier Application Circuit
20060305
FIGURE 2. Bridged Amplifier Application Circuit
LM4731
www.national.com
4
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