LM4878
1 Watt Audio Power Amplifier in micro SMD package
with Shutdown Logic Low
General Description
The LM4878 is a bridge-connected audio power amplifier
capable of delivering 1 W of continuous average power to an
8
load with less than .2% (THD) from a 5V power supply.
Boomer audio power amplifiers were designed specifically to
provide high quality output power with a minimal amount of
external components. Since the LM4878 does not require
output coupling capacitors or bootstrap capacitors. It is op-
timally suited for low-power portable applications.
The LM4878 features an externally controlled, low-power
consumption shutdown mode, as well as an internal thermal
shutdown protection mechanism.
The unity-gain stable LM4878 can be configured by external
gain-setting resistors.
Key Specifications
j
Power Output at 0.2% THD
1 W (typ)
j
Shutdown Current
0.01 A (typ)
Features
n
Internal pulldown resistor on shutdown.
n
micro SMD package (see App. note AN-1112)
n
5V - 2V operation
n
No output coupling capacitors or bootstrap capacitors.
n
Unity-gain stable
n
External gain configuration capability
Applications
n
Cellular Phones
n
Portable Computers
n
Low Voltage Audio Systems
Typical Application
Boomer
is a registered trademark of National Semiconductor Corporation.
10136001
FIGURE 1. Typical Audio Amplifier Application Circuit
October 2002
LM4878
1
W
att
Audio
Power
Amplifier
in
micro
SMD
package
with
Shutdown
Logic
Low
2002 National Semiconductor Corporation
DS101360
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
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)
2500V
ESD Susceptibility (Note 5)
250V
Junction Temperature
150C
Soldering Information
See AN-1112 'Micro-SMD Wafers Level Chip Scale
Package'.
Operating Ratings
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
85C
Supply Voltage
2.0V
V
DD
5.5V
Electrical Characteristics V
DD
= 5V
(Notes 1, 2, 9)
The following specifications apply for V
DD
= 5V and 8
Load unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4878
Units
(Limits)
Typical
Limit
(Note 6)
(Note 7)
V
DD
Supply Voltage
2.0
V (min)
5.5
V (max)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, I
o
= 0A
5.3
7
mA (max)
I
SD
Shutdown Current
V
PIN5
= 0V
0.01
2
A (max)
V
OS
Output Offset Voltage
V
IN
= 0V
5
50
mV (max)
P
o
Output Power
THD = 0.2% (max); f = 1 kHz
1
W
THD+N
Total Harmonic Distortion+Noise
P
o
= 0.25 Wrms; A
VD
= 2; 20 Hz
f
20 kHz
0.1
%
PSRR
Power Supply Rejection Ratio
V
DD
= 4.9V to 5.1V
65
dB
Electrical Characteristics V
DD
= 3.3V
(Notes 1, 2, 9)
The following specifications apply for V
DD
= 3.3V and 8
Load unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4878
Units
(Limits)
Typical
Limit
(Note 6)
(Note 7)
V
DD
Supply Voltage
2.0
V (min)
5.5
V (max)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, I
o
= 0A
4
mA (max)
I
SD
Shutdown Current
V
PIN5
= 0V
0.01
A (max)
V
OS
Output Offset Voltage
V
IN
= 0V
5
mV (max)
P
o
Output Power
THD = 1% (max); f = 1 kHz
.5
.45
W
THD+N
Total Harmonic Distortion+Noise
P
o
= 0.25 Wrms; A
VD
= 2; 20 Hz
f
20 kHz
0.15
%
PSRR
Power Supply Rejection Ratio
V
DD
= 3.2V to 3.4V
65
dB
Electrical Characteristics V
DD
= 2.6V
(Notes 1, 2, 8, 9)
The following specifications apply for V
DD
= 2.6V and 8
Load unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4878
Units
(Limits)
Typical
Limit
(Note 6)
(Note 7)
V
DD
Supply Voltage
2.0
V (min)
5.5
V (max)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, I
o
= 0A
3.4
mA (max)
I
SD
Shutdown Current
V
PIN5
= 0V
0.01
A (max)
LM4878
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3
Electrical Characteristics V
DD
= 2.6V
(Notes 1, 2, 8, 9)
The following specifications apply for V
DD
= 2.6V and 8
Load unless otherwise specified. Limits apply for T
A
=
25C. (Continued)
Symbol
Parameter
Conditions
LM4878
Units
(Limits)
Typical
Limit
(Note 6)
(Note 7)
V
OS
Output Offset Voltage
V
IN
= 0V
5
mV (max)
P
0
Output Power ( 8
)
Output Power ( 4
)
THD = 0.3% (max); f = 1 kHz THD
= 0.5% (max); f = 1 kHz
0.25
0.5
W
W
THD+N
Total Harmonic Distortion+Noise
P
o
= 0.25 Wrms; A
VD
= 2; 20 Hz
f
20 kHz
0.25
%
PSRR
Power Supply Rejection Ratio
V
DD
= 2.5V to 2.7V
65
dB
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 Absolute Maximum Ratings, whichever is lower. For the LM4878, T
JMAX
= 150C.
The typical junction-to-ambient thermal resistance is 150C/W.
Note 4: Human body model, 100 pF discharged through a 1.5 k
resistor.
Note 5: Machine Model, 220 pF240 pF 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: Low Voltage Circuit - See Fig. 4
Note 9: Shutdown current is measured in a Normal Room Environment. Exposure to direct sunlight will increase I
SD
by a maximum of 2A.
Electrical Characteristics V
DD
= 5/3.3/2.6V Shutdown Input
Symbol
Parameter
Conditions
LM4878
Units
(Limits)
Typical
Limit
V
IH
Shutdown Input Voltage High
1.2
V(min)
V
IL
Shutdown Input Voltage Low
0.4
V(max)
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 amplifiers 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 section, Proper Selection of External
Components, for information concerning proper placement and selection of C
B
.
LM4878
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