LM4755
Stereo 11W Audio Power Amplifier with Mute
General Description
The LM4755 is a stereo audio amplifier capable of delivering
11W per channel of continuous average output power to a
4
load or 7W per channel into 8
using a single 24V supply
at 10% THD+N. The internal mute circuit and pre-set gain
resistors provide for a very economical design solution.
Output power specifications at both 20V and 24V supplies
and low external component count offer high value to con-
sumer electronic manufacturers for stereo TV and compact
stereo applications. The LM4755 is specifically designed for
single supply operation.
Key Specifications
n
Output power at 10% THD with 1kHz into 4
at
V
CC
= 24V:
11W (typ)
n
Output power at 10% THD with 1kHz into 8
at
V
CC
= 24V:
7W (typ)
n
Closed loop gain:
34dB (typ)
n
P
O
at 10% THD+N
@
1kHz into 4
single-ended
TO-263 package at V
CC
=12V:
2.5W (typ)
n
P
O
at 10% THD+N
@
1kHz into 8
bridged TO-263
package at V
CC
=12V:
5W (typ)
Features
n
Drives 4
and 8
loads
n
Integrated mute function
n
Internal Gain Resistors
n
Minimal external components needed
n
Single supply operation
n
Internal current limiting and thermal protection
n
Compact 9-lead TO-220 package
n
Wide supply range 9V - 40V
Applications
n
Stereos TVs
n
Compact stereos
n
Mini component stereos
Typical Application
Connection Diagrams
DS100059-1
FIGURE 1. Typical Audio Amplifier Application Circuit
Plastic Package
DS100059-2
Package Description
Top View
Order Number LM4755T
Package Number TA09A
DS100059-36
Top View
Order Number LM4755TS
Package Number TS9A
May 2002
LM4755
Stereo
1
1
W
Audio
Power
Amplifier
with
Mute
2002 National Semiconductor Corporation
DS100059
www.national.com
Absolute Maximum Ratings
(Note 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage
40V
Input Voltage
0.7V
Output Current
Internally Limited
Power Dissipation (Note 3)
62.5W
ESD Susceptability (Note 4)
2 kV
Junction Temperature
150C
Soldering Information
T Package (10 seconds)
250C
Storage Temperature
-40C to 150C
Operating Ratings
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
+85C
Supply Voltage
9V to 32V
JC
2C/W
JA
76C/W
Electrical Characteristics
The following specifications apply to each channel with V
CC
= 24V, T
A
= 25C unless otherwise specified.
Symbol
Parameter
Conditions
LM4755
Units
(Limits)
Typical
(Note 5)
Limit
I
TOTAL
Total Quiescent Power
Supply Current
Mute Off
10
15
mA(max)
7
mA(min)
Mute On
7
mA
P
O
Output Power (Continuous
Average per Channel)
f = 1 kHz, THD+N = 10%, R
L
= 8
7
W
f = 1 kHz, THD+N = 10%, R
L
= 4
11
10
W(min)
V
S
= 20V, R
L
= 8
4
W
V
S
= 20V, R
L
= 4
7
W
f = 1 kHz, THD+N = 10%, R
L
= 4
V
S
= 12V, TO-263 Pkg.
2.5
W
THD
Total Harmonic Distortion
f = 1 kHz, P
O
= 1 W/ch, R
L
= 8
0.08
%
V
OSW
Output Swing
P
O
= 10W, R
L
= 8
15
V
P
O
= 10W, R
L
= 4
14
V
X
TALK
Channel Separation
See Apps. Circuit
55
dB
f = 1 kHz, V
O
= 4 Vrms
PSRR
Power Supply Rejection Ratio
See Apps. Circuit
50
dB
f = 120 Hz, V
O
= 1 mVrms
V
ODV
Differential DC Output Offset
Voltage
V
IN
= 0V
0.09
0.4
V(max)
SR
Slew Rate
2
V/s
R
IN
Input Impedance
83
k
PBW
Power Bandwidth
3 dB BW at P
O
= 2.5W, R
L
= 8
65
kHz
A
VCL
Closed Loop Gain
(Internally Set)
R
L
= 8
34
33
dB(min)
35
dB(max)
e
IN
Noise
IHF-A Weighting Filter, R
L
= 8
Output Referred
0.2
mVrms
I
O
Output Short Circuit Limit
V
IN
= 0.5V, R
L
= 2
2
A(min)
Mute Pin
V
IL
Mute Low Input Voltage
Not in Mute Mode
0.8
V(max)
V
IH
Mute High Input Voltage
In Mute Mode
2.0
2.5
V(min)
A
M
Mute Attenuation
V
MUTE
= 5.0V
80
dB
Note 1: All voltages are measured with respect to the GND pin (5), unless otherwse 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 device performance.
Note 3: For operating at case temperatures above 25C, the device must be derated based on a 150C maximum junction temperature and a thermal resistance
of
JC
= 2C/W (junction to case). Refer to the section Determining the Maximum Power Dissipation in the Application Information section for more information.
Note 4: Human body model, 100 pF discharged through a 1.5 k
resistor.
LM4755
www.national.com
2
Electrical Characteristics
(Continued)
Note 5: Typicals are measured at 25C and represent the parametric norm.
Note 6: Limits are guaranteed that all parts are tested in production to meet the stated values.
Note 7: The TO-263 Package is not recommended for V
S
>
16V due to impractical heatsinking limitations.
Equivalent Schematic
DS100059-3
LM4755
www.national.com
3
System Application Circuit
External Components Description
Components
Function Description
1, 2
C
S
Provides power supply filtering and bypassing.
3, 4
R
SN
Works with C
SN
to stabilize the output stage from high frequency oscillations.
5, 6
C
SN
Works with R
SN
to stabilize the output stage from high frequency oscillations.
7
C
b
Provides filtering for the internally generated half-supply bias generator.
8, 9
C
i
Input AC coupling capacitor which blocks DC voltage at the amplifier's input terminals. Also creates a
high pass filter with fc=1/(2
Rin
Cin).
10, 11
C
o
Output AC coupling capacitor which blocks DC voltage at the amplifier's output terminal. Creates a high
pass filter with fc=1/(2
Rout
Cout).
12, 13
R
i
Voltage control - limits the voltage level allowed to the amplifier's input terminals.
14
R
m
Works with C
m
to provide mute function timing.
15
C
m
Works with R
m
to provide mute function timing.
DS100059-5
FIGURE 3. Circuit for External Components Description
LM4755
www.national.com
5
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