LM4818
350mW Audio Power Amplifier with Shutdown Mode
General Description
The LM4818 is a mono bridged power amplifier that is ca-
pable of delivering 350mW
RMS
output power into a 16
load
or 300mW
RMS
output power into an 8
load with 10%
THD+N from a 5V power supply.
The LM4818 Boomer audio power amplifier is designed
specifically to provide high quality output power and mini-
mize PCB area with surface mount packaging and a minimal
amount of external components. Since the LM4818 does not
require output coupling capacitors, bootstrap capacitors or
snubber networks, it is optimally suited for low-power por-
table applications.
The closed loop response of the unity-gain stable LM4818
can be configured using external gain-setting resistors. The
device is available in SO package type to suit various appli-
cations.
Key Specifications
n
THD+N at 1kHz, 350mW continuous average output
power into 16
10% (max)
n
THD+N at 1kHz, 300mW continuous average output
power into 8
10% (max)
n
Shutdown Current
0.7A (typ)
Features
n
SOP surface mount packaging.
n
Switch on/off click suppression.
n
Unity-gain stable.
n
Minimum external components.
Applications
n
General purpose audio
n
Portable electronic devices
n
Information Appliances (IA)
Typical Application
Boomer
is a registered trademark of National Semiconductor Corporation.
DS200389-1
FIGURE 1. Typical Audio Amplifier Application Circuit
April 2002
LM4818
350mW
Audio
Power
Amplifier
with
Shutdown
Mode
2002 National Semiconductor Corporation
DS200389
www.national.com
Absolute Maximum Ratings
(Notes 2, 3)
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 (P
D
) (Note 4)
Internally Limited
ESD Susceptibility (Note 5)
2.5kV
ESD Susceptibility (Note 6)
200V
Junction Temperature (T
J
)
150C
Soldering Information (Note 1)
Small Outline Package
Vapor Phase (60 seconds)
215C
Infrared (15 seconds)
220C
Thermal Resistance
JC
(SOP)
35C/W
JA
(SOP)
170C/W
Operating Ratings
(Notes 2, 3)
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
85C
Supply Voltage
2.0V
V
CC
5.5V
Electrical Characteristics V
DD
= 5V
(Notes 2, 3)
The following specifications apply for V
DD
= 5V, R
L
= 16
unless otherwise stated. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4818
Units
(Limits)
Typical
Limit
(Note 7)
(Notes 8, 9)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, I
o
= 0A
1.5
3.0
mA (max)
I
SD
Shutdown Current
V
PIN1
= V
DD
(Note 10)
1.0
5.0
A (max)
I
SDIH
Shutdown Voltage Input High
4.0
V (min)
I
SDIL
Shutdown Voltage Input Low
1.0
V (max)
V
OS
Output Offset Voltage
V
IN
= 0V
5
50
mV (max)
P
O
Output Power
THD = 10%, f
IN
= 1kHz
350
mW
THD = 10%, f
IN
= 1kHz, R
L
= 8
300
mW
THD+N
Total Harmonic Distortion + Noise
P
O
= 270mW
RMS
, A
VD
= 2, f
IN
=
1kHz
1
%
Electrical Characteristics V
DD
= 3V
(Notes 2, 3)
The following specifications apply for V
DD
= 3V and R
L
= 16
load unless otherwise stated. Limits apply to T
A
= 25C.
Symbol
Parameter
Conditions
LM4818
Units
(Limits)
Typical
Limit
(Note 7)
(Notes 8, 9)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, I
o
= 0A
1.0
3.0
mA (max)
I
SD
Shutdown Current
V
PIN1
= V
DD
(Note 10)
0.7
5.0
A (max)
I
SDIH
Shutdown Voltage Input High
2.4
V (min)
I
SDIL
Shutdown Voltage Input Low
0.6
V (max)
V
OS
Output Offset Voltage
V
IN
= 0V
5
50
mV
P
O
Output Power
THD = 10%, f
IN
= 1kHz
110
mW
THD = 10%, f
IN
= 1kHz, R
L
= 8
90
mW
THD+N
Total Harmonic Distortion + Noise
P
O
= 80mW
RMS
, A
VD
= 2, f
IN
=
1kHz
1
%
LM4818
www.national.com
3
Electrical Characteristics V
DD
= 3V
(Notes 2, 3)
The following specifications apply for V
DD
= 3V and R
L
= 16
load unless otherwise stated. Limits apply to T
A
=
25C. (Continued)
Note 1: See AN-450 'Surface Mounting and their Effects on Product Reliability' for other methods of soldering surface mount devices.
Note 2: All voltages are measured with respect to the ground pin, unless otherwise specified.
Note 3:
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's performance.
Note 4: 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
. For the LM4818, T
JMAX
= 150C and the typical junction-to-ambient thermal resistance (
JA
) when board
mounted is 170C/W for the SOP package.
Note 5: Human body model, 100pF discharged through a 1.5 k
resistor.
Note 6: Machine Model, 220pF240pF capacitor is discharged through all pins.
Note 7: Typical specifications are specified at 25C and represent the parametric norm.
Note 8: Tested limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
Note 9: Datasheet min/max specification limits are guaranteed by designs, test, or statistical analysis.
Note 10: The Shutdown pin (pin 1) should be driven as close as possible to V
DD
for minimum current in Shutdown Mode.
External Components Description
(
Figure 1)
Components
Functional Description
1.
R
i
Combined with R
f
, this inverting input resistor sets the closed-loop gain. R
i
also forms a high pass filter with
C
i
at f
c
= 1/(2
R
i
C
i
).
2.
C
i
This input coupling capacitor blocks DC voltage at the amplifier's terminals. Combined with R
i
, it creates a
high pass 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
Combined with R
i
, this is the feedback resistor that sets the closed-loop gain: A
v
= 2(R
F
/R
i
).
4.
C
S
This is the power supply bypass capacitor that filters the voltage applied to the power supply pin. Refer to
the Application Information section for proper placement and selection of C
s
.
5.
C
B
This is the bypass pin capacitor that filters the voltage at the BYPASS pin. Refer to the section, Proper
Selection of External Components for information concerning proper placement and selection of C
B
.
6.
C
B2
This is an optional capacitor that is not needed in the majority of applications. If the capacitor is not used,
pin 3 should be connected directly to pin2. Refer to the section Proper Selection of External Components
for more information concerning C
B2
.
Typical Performance Characteristics
DS200389-37
DS200389-38
LM4818
www.national.com
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