LM4902
265mW at 3.3V Supply Audio Power Amplifier with
Shutdown Mode
General Description
The LM4902 is a bridged audio power amplifier capable of
delivering 265mW of continuous average power into an 8
load with 1% THD+N from a 3.3V power supply.
Boomer
audio power amplifiers were designed specifically
to provide high quality output power from a low supply volt-
age while requiring a minimal amount of external compo-
nents. Since the LM4902 does not require output coupling
capacitors, bootstrap capacitors or snubber networks, it is
optimally suited for low-power portable applications.
The LM4902 features an externally controlled, low power
consumption shutdown mode, and thermal shutdown protec-
tion.
The closed loop response of the unity-gain stable LM4902
can be configured by external gain-setting resistors.
Key Specifications
j
THD+N at 1kHz for 265mW continuous
average output power into 8
,
V
DD
= 3.3V
1.0% (max)
j
THD+N at 1kHz for 675mW continuous
average output power into 8
,
V
DD
= 5V
1.0% (max)
j
Shutdown current
0.1A (typ)
Features
n
MSOP and LLP packaging
n
No output coupling capacitors, bootstrap capacitors, or
snubber circuits are necessary
n
Thermal shutdown protection circuitry
n
Unity-gain stable
n
External gain configuration capability
n
Latest generation 'click and pop' suppression circuitry
Applications
n
Cellular phones
n
PDA's
n
Any portable audio application
Typical Application
Boomer
is a registered trademark of National Semiconductor Corporation.
20029801
FIGURE 1. Typical Audio Amplifier Application Circuit
February 2002
LM4902
265mW
at
3.3V
Supply
Audio
Power
Amplifier
with
Shutdown
Mode
2002 National Semiconductor Corporation
DS200298
www.national.com
Connection Diagrams
MSOP
MSOP Marking
20029802
Top View
Order Number LM4902MM
See NS Package Number MUA08A
20029878
Top View
G - Boomer Family
C3 - LM4902MM
LLP
LLP Marking
20029875
Top View
Order Number LM4902LD
See NS Package Number LDA08B
20029877
Top View
XY - Date Code
TT - Die Traceability
G - Boomer Family
A3 - LM4902LD
LM4902
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2
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
6.0V
Storage Temperature
-65C to +150C
Input Voltage
-0.3V to V
DD
+ 0.3V
Power Dissipation (Note 3)
Internally limited
ESD Susceptibility (Note 4)
2000V
ESD Susceptibility (Note 5)
200V
Junction Temperature
150C
Soldering Information
Small Outline Package
Vapor Phase (60 sec.)
215C
Infrared (15 sec.)
220C
See AN-450 "Surface Mounting and their Effects on
Product Reliability" for other methods of soldering surface
mount devices.
Thermal Resistance
JC
(MSOP)
56C/W
JA
(MSOP)
190C/W
JA
(LLP)
67C/W
Operating Ratings
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
+85C
Supply Voltage
2.0V
V
DD
5.5V
Electrical Characteristics
(Note 1) (Note 2)
The following specifications apply for V
DD
= 5V, for all available packages, unless otherwise specified. Limits apply for T
A
=
25C
Symbol
Parameter
Conditions
LM4902
Units
(Limits)
Typical
(Note 6)
Limit
(Notes 7,
9)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, I
O
= 0A (Note 8)
4
6.0
mA (max)
I
SD
Shutdown Current
V
PIN1
=GND
0.1
5
A (max)
V
OS
Output Offset Voltage
V
IN
= 0V
5
50
mV (max)
P
O
Output Power
THD = 1% (max); f = 1kHz; R
L
= 8
;
675
300
mW (min)
THD+N
Total Harmonic Distortion+Noise
P
O
= 400 mWrms; A
VD
= 2; R
L
= 8
;
20Hz
f
20kHz, BW
<
80kHz
0.4
%
PSRR
Power Supply Rejection Ratio
V
RIPPLE
= 200mV sine p-p
dB
f = 217Hz (Note 10)
70
f = 1KHz (Note 10)
67
f = 217Hz (Note 11)
55
f = 1KHz (Note 11)
55
Electrical Characteristics
(Notes 1, 2)
The following specifications apply for V
DD
= 3.3V, for all available packages, unless otherwise specified. Limits apply for T
A
=
25C
Symbol
Parameter
Conditions
LM4902
Units
(Limits)
Typical
(Note 6)
Limit
(Notes 7,
9)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, I
O
= 0A (Note 8)
3
5
mA (max)
I
SD
Shutdown Current
V
PIN1
= GND
0.1
3
A (max)
V
OS
Output Offset Voltage
V
IN
= 0V
5
50
mV (max)
P
O
Output Power
THD = 1% (max); f = 1kHz; R
L
= 8
;
265
mW
THD+N
Total Harmonic Distortion+Noise
P
O
= 250 mWrms; A
VD
= 2; R
L
= 8
;
20Hz
f
20kHz, BW
<
80kHz
0.4
%
PSRR
Power Supply Rejection Ratio
V
RIPPLE
= 200mV sine p-p
dB
f = 217Hz (Note 10)
73
f = 1KHz (Note 10)
70
f = 217Hz (Note 11)
60
f = 1KHz (Note 11)
68
LM4902
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3
Electrical Characteristics
(Notes 1, 2)
The following specifications apply for V
DD
= 2.6V, for all available packages, unless otherwise specified. Limits apply for T
A
=
25C
Symbol
Parameter
Conditions
LM4902
Units
(Limits)
Typical
(Note 6)
Limit
(Notes 7,
9)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, I
O
= 0A (Note 8)
2.6
4
mA (max)
I
SD
Shutdown Current
V
PIN1
= V
DD
0.1
2.0
A (max)
V
OS
Output Offset Voltage
V
IN
= 0V
5
mV
P
O
Output Power
THD = 1% (max); f = 1kHz; R
L
= 8
130
mW
THD+N
Total Harmonic Distortion+Noise
P
O
= 100 mWrms; A
VD
= 2; R
L
= 8
;
20Hz
f
20kHz, BW
<
80kHz
0.4
%
PSRR
Power Supply Rejection Ratio
V
RIPPLE
= 200mV sine p-p
dB
f = 217Hz (Note 11)
58
f = 1KHz (Note 11)
63
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 device performance.
Note 3: The maximum power dissipation must be derated at elevated temperatures and is dictated by T
JMAX
,
JA
, and the ambient temperature T
A
. The maximum
allowable power dissipation is P
DMAX
= (T
JMAX
- T
A
)/
JA
or the number given in the Absolute Maximum Ratings, whichever is lower. For the LM4902, T
JMAX
=
150C. The typical junction-to-ambient thermal resistance, when board mounted, is 190C/W for package number MUA08A.
Note 4: Human body model, 100pF discharged through a 1.5k
resistor.
Note 5: Machine Model, 220pF240pF discharged through all pins.
Note 6: Typicals are measured at 25C and represent the parametric norm.
Note 7: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
Note 8: The quiescent power supply current depends on the offset voltage when a practical load is connected to the amplifier.
Note 9: Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis.
Note 10: Unterminated input.
Note 11: 10
terminated input.
LM4902
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4
External Components Description
(Figure 1)
Components
Functional Description
1.
R
i
Inverting input resistance which sets the closed-loop gain in conjunction with R
F
. This resistor also forms a
high pass filter with C
i
at f
c
= 1/(2
R
i
C
I
).
2.
C
i
Input coupling capacitor which blocks the DC voltage at the amplifier's input terminals. Also creates a
highpass filter with R
i
at f
c
= 1/(2
R
i
C
i
). Refer to the section, Proper Selection of External Components,
for an explanation of how to determine the value of C
i
.
3.
R
F
Feedback resistance which sets the closed-loop gain in conjunction with R
i
.
4.
C
S
Supply bypass capacitor which provides power supply filtering. Refer to the Power Supply Bypassing
section for information concerning proper placement and selection of the supply bypass capacitor.
5.
C
B
Bypass pin capacitor which provides half-supply filtering. Refer to the Proper Selection of External
Components for information concerning proper placement and selection of C
B
.
Typical Performance
Characteristics
THD+N vs Frequency
THD+N vs Frequency
20029830
20029831
THD+N vs Frequency
THD+N vs Frequency
20029832
20029833
LM4902
www.national.com
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