LM4941
1.25 Watt Fully Differential Audio Power Amplifier With
RF Suppression and Shutdown
General Description
The LM4941 is a fully differential audio power amplifier
primarily designed for demanding applications in mobile
phones and other portable communication device applica-
tions. It is capable of delivering 1.25 watts of continuous
average power to a 8
load with less than 1% distortion
(THD+N) from a 5V
DC
power supply. The LM4941 does not
require output coupling capacitors or bootstrap capacitors,
and therefore is ideally suited for mobile phone and other low
voltage applications where minimal power consumption is a
primary requirement.
The LM4941 also features proprietary internal circuitry that
suppresses the coupling of RF signals into the chip. This is
important because certain types of RF signals (such as
GSM) can couple into audio amplifiers in such a way that
part of the signal is heard through the speaker. The RF
suppression circuitry in the LM4941 makes it well-suited for
portable applications in which strong RF signals generated
by an antenna from or a cellular phone or other portable
electronic device may couple audibly into the amplifier.
Other features include a low-power consumption shutdown
mode, internal thermal shutdown protection, and advanced
pop & click circuitry.
Key Specifications
j
Improved PSRR at 217Hz
95dB (typ)
j
Power Output at 5.0V
@
1% THD (8
)
1.25W (typ)
j
Power Output at 3.3V
@
1% THD
550mW (typ)
j
Shutdown Current
0.1A (typ)
Features
n
Improved RF suppression, by up to 20dB over previous
designs in selected applications
n
Fully differential amplification
n
Available in space-saving micro SMD package
n
Ultra low current shutdown mode
n
Can drive capacitive loads up to 100pF
n
Improved pop & click circuitry eliminates noises during
turn-on and turn-off transitions
n
2.4 - 5.5V operation
n
No output coupling capacitors, snubber networks or
bootstrap capacitors required
Applications
n
Mobile phones
n
PDAs
n
Portable electronic devices
Typical Application
Boomer
is a registered trademark of National Semiconductor Corporation.
20170303
FIGURE 1. Typical Audio Amplifier Application Circuit
June 2006
LM4941
1.25
W
att
Fully
Differential
Audio
Power
Amplifier
W
ith
RF
Suppression
and
Shutdown
2006 National Semiconductor Corporation
DS201703
www.national.com
Connection Diagrams
9 Bump micro SMD Package
20170304
Top View
Order Number LM4941TM
See NS Package Number TMD09AAA
micro SMD Marking
20170302
Top View
X = Date Code
V = Die Traceability
G = Boomer Family
H6 = LM4941TM
LM4941
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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
Thermal Resistance
JA
(TM)
100C/W
Soldering Information
See AN-1187
Operating Ratings
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
85C
Supply Voltage
2.4V
V
DD
5.5V
Electrical Characteristics V
DD
= 5V
(Notes 1, 2)
The following specifications apply for V
DD
= 5V, A
V
= 1, and 8
load unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4941
Units
(Limits)
Typical
Limit
(Note 6)
(Note 7)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, no load
V
IN
= 0V, R
L
= 8
1.7
1.7
2.5
mA (max)
I
SD
Shutdown Current
V
SHUTDOWN
= GND
0.1
1
A (max)
P
o
Output Power
THD = 1% (max); f = 1 kHz
R
L
= 8
1.25
1.1
W (min)
THD = 10% (max); f = 1 kHz
R
L
= 8
1.54
W
THD+N
Total Harmonic Distortion + Noise
P
o
= .7 Wrms; f = 1kHz
.04
%
PSRR
Power Supply Rejection Ratio
V
ripple
= 200mV sine p-p
f = 217Hz (Note 8)
95
70
dB (min)
f = 1kHz (Note 8)
90
CMRR
Common-Mode Rejection Ratio
f = 217Hz, V
CM
= 200mV
pp
70
dB
f = 20Hz20kHz , V
CM
= 200mV
pp
70
dB
V
OS
Output Offset
V
IN
= 0V
2
mV
V
SDIH
Shutdown Voltage Input High
1.4
V (min)
V
SDIL
Shutdown Voltage Input Low
0.4
V (max)
SNR
Signal-to-Noise Ratio
P
O
= 1W, f = 1kHz
108
dB
T
WU
Wake-up Time from Shutdown
Cbypass = 1F
12
ms
Electrical Characteristics V
DD
= 3V
(Notes 1, 2)
The following specifications apply for V
DD
= 3V, A
V
= 1, and 8
load unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4941
Units
(Limits)
Typical
Limit
(Note 6)
(Note 7)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, no load
V
IN
= 0V, R
L
= 8
1.6
1.6
2.4
mA (max)
I
SD
Shutdown Current
V
SHUTDOWN
= GND
0.1
1
A (max)
P
o
Output Power
THD = 1% (max); f = 1 kHz
R
L
= 8
0.43
W
THD = 10% (max); f = 1 kHz
R
L
= 8
0.54
W
THD+N
Total Harmonic Distortion + Noise
P
o
= 0.25Wrms; f = 1kHz
.05
%
PSRR
Power Supply Rejection Ratio
V
ripple
= 200mV sine p-p
f = 217Hz (Note 8)
95
dB
f = 1kHz (Note 8)
90
LM4941
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3
Electrical Characteristics V
DD
= 3V
(Notes 1, 2)
The following specifications apply for V
DD
= 3V, A
V
= 1, and 8
load unless otherwise specified. Limits apply for T
A
=
25C. (Continued)
Symbol
Parameter
Conditions
LM4941
Units
(Limits)
Typical
Limit
(Note 6)
(Note 7)
CMRR
Common-Mode Rejection Ratio
f = 217Hz, V
CM
= 200mV
pp
70
dB
V
OS
Output Offset
V
IN
= 0V
2
mV (max)
V
SDIH
Shutdown Voltage Input High
1.4
V (min)
V
SDIL
Shutdown Voltage Input Low
0.4
V (max)
T
WU
Wake-up Time from Shutdown
Cbypass
8
ms
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 LM4941, see power
derating curve for additional information.
Note 4: Human body model, 100pF discharged through a 1.5k
resistor.
Note 5: Machine Model, 220pF 240pF 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: 10
terminated input.
Note 9: Data taken with BW = 80kHz and A
V
= 1/1 except where specified.
External Components Description
(Figure 1)
Components
Functional Description
1.
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.
2.
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
.
3.
R
i
Inverting input resistance which sets the closed-loop gain in conjunction with R
f
.
4.
R
f
Internal feedback resistance which sets the closed-loop gain in conjunction with R
i
.
LM4941
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4
Typical Performance Characteristics
(Note 9)
THD+N vs Output Power
V
DD
= 5V, R
L
= 8
, f = 1kHz
THD+N vs Output Power
V
DD
= 3V, R
L
= 8
, f = 1kHz
20170305
20170306
THD+N vs Frequency
V
DD
= 5V, R
L
= 8
, P
O
= 700mW
THD+N vs Frequency
V
DD
= 3V, R
L
= 8
, P
O
= 250mW
20170307
20170308
PSRR vs Frequency
V
DD
= 5V, R
L
= 8
, Inputs terminated
PSRR vs Frequency
V
DD
= 3V, R
L
= 8
, Inputs terminated
20170309
20170310
LM4941
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