LM4905
1 Watt Audio Power Amplifier
General Description
The LM4905 is an audio power amplifier primarily designed
for demanding applications in mobile phones and other por-
table communication device applications. It is capable of
delivering 1 watt of continuous average power to an 8
BTL
load with less than 1% distortion (THD+N) from a 5V
DC
power supply.
Boomer audio power amplifiers were designed specifically to
provide high quality output power with a minimal amount of
external components. The LM4905 does not require output
coupling capacitors or bootstrap capacitors, and therefore is
ideally suited for mobile phone and other low voltage appli-
cations where minimal power consumption is a primary re-
quirement.
The LM4905 features a low-power consumption shutdown
mode, which is achieved by driving the shutdown pin with
logic low. Additionally, the LM4905 features an internal ther-
mal shutdown protection mechanism.
The LM4905 contains advanced pop & click circuitry which
eliminates noise which would otherwise occur during turn-on
and turn-off transitions.
The LM4905 is unity-gain stable and can be configured by
external gain-setting resistors.
Key Specifications
j
Improved PSRR at 217Hz & 1KHz
62dB
j
Power Output at 5.0V, 1% THD, 8
1.07W (typ)
j
Power Output at 3.0V, 1% THD, 8
390mW (typ)
j
Shutdown Current
0.1A (typ)
Features
n
Available in space-saving LLP package
n
Ultra low current shutdown mode
n
BTL output can drive capacitive loads
n
Improved pop & click circuitry eliminates noise during
turn-on and turn-off transitions
n
2.2 - 5.5V operation
n
No output coupling capacitors, snubber networks or
bootstrap capacitors required
n
Unity-gain stable
n
External gain configuration capability
Applications
n
Mobile Phones
n
PDAs
n
Portable electronic devices
Typical Application
Boomer
is a registered trademark of National Semiconductor Corporation.
200508D3
FIGURE 1. Typical Audio Amplifier Application Circuit
July 2003
LM4905
1
W
att
Audio
Power
Amplifier
2003 National Semiconductor Corporation
DS200508
www.national.com
Connection Diagrams
LD Package
200508E1
Top View
Order Number LM4905LD
See NS Package Number LDA08A
LQ Package
20050802
Top View
Order Number LM4905LQ
See NS Package Number LQB08A
Mini Small Outline (MSOP) Package
20050801
Top View
Order Number LM4905MM
See NS Package Number MUA08A
LM4905
www.national.com
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 (Note 10)
6.0V
Storage Temperature
-65C to +150C
Input Voltage
-0.3V to V
DD
+0.3V
Power Dissipation (Notes 3, 11)
Internally Limited
ESD Susceptibility (Note 4)
2000V
ESD Susceptibility (Note 5)
200V
Junction Temperature
150C
Thermal Resistance
JC
(LQ)
57C/W
JA
(LQ)
140C/W
JC
(LD)
71C/W
JA
(LD)
95C/W
Operating Ratings
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
85C
Supply Voltage
2.2V
V
DD
5.5V
Electrical Characteristics V
DD
= 5V
(Notes 1, 2)
The following specifications apply for the circuit shown in Figure 1, unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4905
Units
(Limits)
Typical
Limit
(Note 6)
(Notes 7, 8)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, I
o
= 0A, No Load
3.4
7
mA (max)
V
IN
= 0V, I
o
= 0A, 8
Load
4
10
mA (max)
I
SD
Shutdown Current
V
SD
= V
GND
0.8
2
A (max)
V
SDIH
Shutdown Voltage Input High
1.5
V (min)
V
SDIL
Shutdown Voltage Input Low
1.3
V (max)
V
OS
Output Offset Voltage
7
50
mV (max)
P
o
Output Power
THD = 1% (max); f = 1 kHz
1.07
0.9
W
T
WU
Wake-up time
100
mS (max)
THD+N
Total Harmonic Distortion+Noise
P
o
= 0.5 Wrms; f = 1kHz
0.2
%
PSRR
Power Supply Rejection Ratio
V
ripple
= 200mV sine p-p
Input terminated with 10
60 (f =
217Hz)
64 (f = 1kHz)
55
dB (min)
Electrical Characteristics V
DD
= 3V
(Notes 1, 2)
The following specifications apply for the circuit shown in Figure 1, unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4905
Units
(Limits)
Typical
Limit
(Note 6)
(Notes 7, 8)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, I
o
= 0A, No Load
2.4
7
mA (max)
V
IN
= 0V, I
o
= 0A, 8
Load
3
9
mA (max)
I
SD
Shutdown Current
V
SD
= V
GND
0.1
1.0
A (max)
V
SDIH
Shutdown Voltage Input High
1.3
V (min)
V
SDIL
Shutdown Voltage Input Low
1.0
V (max)
V
OS
Output Offset Voltage
7
50
mV (max)
P
o
Output Power
THD = 1% (max); f = 1 kHz
390
mW
T
WU
Wake-up time
75
mS (max)
THD+N
Total Harmonic Distortion+Noise
P
o
= 0.25 Wrms; f = 1kHz
0.1
%
PSRR
Power Supply Rejection Ratio
V
ripple
= 200mV sine p-p
Input terminated with 10
65 (f =
217Hz)
70 (f = 1kHz)
55
dB (min)
LM4905
www.national.com
3
Electrical Characteristics V
DD
= 2.6V
(Notes 1, 2)
The following specifications apply for the circuit shown in Figure 1, unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4905
Units
(Limits)
Typical
Limit
(Note 6)
(Notes 7, 8)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, I
o
= 0A, No Load
2.0
mA (max)
V
IN
= 0V, I
o
= 0A, 8
Load
3.0
mA (max)
I
SD
Shutdown Current
V
SD
= V
GND
0.01
1.0
A (max)
V
SDIH
Shutdown Voltage Input High
1.2
V (min)
V
SDIL
Shutdown Voltage Input Low
1.0
V (max)
V
OS
Output Offset Voltage
5
50
mV (max)
P
o
Output Power
THD = 1% (max); f = 1 kHz
270
mW
T
WU
Wake-up time
70
mS (max)
THD+N
Total Harmonic Distortion+Noise
P
o
= 0.15 Wrms; f = 1kHz
0.1
%
PSRR
Power Supply Rejection Ratio
V
ripple
= 200mV sine p-p
Input terminated with 10
51 (f =
217Hz)
51 (f = 1kHz)
dB (min)
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 LM4905, see power derating
curves for additional information.
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: Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis.
Note 9: R
OUT
is measured from the output pin to ground. This value represents the parallel combination of the 10k
output resistors and the two 20k resistors.
Note 10: If the product is in Shutdown mode and V
DD
exceeds 6V (to a max of 8V V
DD
), then most of the excess current will flow through the ESD protection circuits.
If the source impedance limits the current to a max of 10mA, then the device will be protected. If the device is enabled when V
DD
is greater than 5.5V and less than
6.5V, no damage will occur, although operation life will be reduced. Operation above 6.5V with no current limit will result in permanent damage.
Note 11: Maximum power dissipation in the device (P
DMAX
) occurs at an output power level significantly below full output power. P
DMAX
can be calculated using
Equation 1 shown in the Application Information section. It may also be obtained from the power dissipation graphs.
LM4905
www.national.com
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 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
.
Typical Performance Characteristics
THD+N vs Frequency
at V
DD
= 5V, 8
R
L
, and PWR = 500mW
THD+N vs Frequency
at V
DD
= 3V, 8
R
L
, and PWR = 250mW
20050830
20050831
THD+N vs Frequency
at V
DD
= 2.6V, 8
R
L
, and PWR = 150mW
THD+N vs Power Out
at V
DD
= 5V, 8
R
L
, 1kHz
20050832
20050834
LM4905
www.national.com
5
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