LM4805
Low Voltage High Power Audio Power Amplifier
General Description
The LM4805 is a boosted audio power amplifier designed for
driving 8ohm speakers in portable applications. It delivers at
least 1W continuous power to an 8
load from any input
voltage between 3V and 4.6V with less than 2% THD+N.
Boomer audio power amplifiers were designed specifically to
provide high quality output power with a minimal amount of
external components. The LM4805 does not require boot-
strap capacitors, or snubber circuits. Therefore it is ideally
suited for portable applications requiring high power and
minimal size.
The LM4805 features a low-power consumption shutdown
mode along with an internal thermal shutdown protection
mechanism and short circuit protection.
The LM4805 contains advanced pop & click circuitry that
eliminates noises which would otherwise occur during
turn-on and turn-off transitions. The LM4805 is unity-gain
stable and can be configured by external gain-setting resis-
tors.
Key Specifications
j
Quiescent Power Supply Current
(V
DD
= 3V)
14mA (typ)
j
Output Power
(V
DD
= 3.0V, R
L
= 8
, THD+N = 2%)
1W (typ)
j
Shutdown Current
2A (max)
Features
n
Pop & click circuitry eliminates noise during turn-on and
turn-off transitions
n
Low, 2A (max) shutdown current
n
Low, 14mA (typ) quiescent current
n
Unity-gain stable
n
External gain configuration capability
Applications
n
Cellphone
n
PTT (Push To Talk) mobile phones
Connection Diagrams
LM4805LQ (5x5)
LQ Marking
20126284
Top View
Order Number LM4805LQ
See NS Package Number LQA28A
20126256
Top View
U = Wafer Fab
Z = Assembly Plant Code
XY = Date Code
TT = Die Run Code
Boomer
is a registered trademark of National Semiconductor Corporation.
August 2005
LM4805
Low
V
oltage
High
Power
Audio
Power
Amplifier
2005 National Semiconductor Corporation
DS201262
www.national.com
Typical Application
20126210
* Cf2 is optional.
FIGURE 1. Typical Audio Amplifier Application Circuit
LM4805
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2
Absolute Maximum Ratings
(Notes 1, 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (V
DD
)
6.5V
Supply Voltage (V
1
)
6.5V
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
125C
Thermal Resistance
JA
(LLP)
59C/W
See AN-1187 'Leadless Leadframe Packaging (LLP).'
Operating Ratings
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
+85C
Supply Voltage (V
DD
)
2.7V
V
DD
4.6V
Supply Voltage (V
1
)
2.7V
V
1
6.1V
Electrical Characteristics V
DD
= 4.2V
(Notes 1, 2)
The following specifications apply for V
DD
= 4.2V, A
V-BTL
= 26dB, R
L
= 8
, C
B
= 1.0F, R
1
= 51.1k
, R
2
= 15k
unless other-
wise specified. Limits apply for T
A
= 25C. See Figure 1.
Symbol
Parameter
Conditions
LM4805
Units
(Limits)
Typical
(Note 6)
Limit
(Notes 7, 8)
I
DD
Quiescent Power Supply Current
V
IN
= 0, R
LOAD
=
10
23
mA (max)
I
SD
Shutdown Current
V
SHUTDOWN
= GND (Notes 9, 10)
0.1
2
A (max)
V
SDIH
Shutdown Voltage Input High
S/D1 and S/D2
1.5
V (min)
V
SDIL
Shutdown Voltage Input Low
S/D1 and S/D2
0.4
V (max)
T
WU
Wake-up Time
C
B
= 1.0F
80
110
msec
(max)
V
OS
Output Offset Voltage
5
40
mV (max)
TSD
Thermal Shutdown Temperature
125
C (min)
P
OUT
Output Power
THD = 1% (max), f = 1kHz,
Mono BTL
1.2
0.9
W (min)
THD+N
Total Harmomic Distortion + Noise
P
O
= 500mW, f = 1kHz
0.2
0.5
% (max)
e
OS
Output Noise
A-Weighted Filter, V
IN
= 0V
105
V
PSRR
Power Supply Rejection Ratio
V
RIPPLE
= 200mV
p-p
, f = 100Hz,
inputs terminated
66
dB
V
FB
Feedback Pin Reference Voltage
Note 11
1.23
V
Electrical Characteristics V
DD
= 3.0V
(Notes 1, 2)
The following specifications apply for V
DD
= 3.0V, A
V-BTL
= 26dB, R
L
= 8
, C
B
= 1.0F, R
1
= 51.1k
, R
2
= 15k
unless other-
wise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4805
Units
(Limits)
Typical
(Note 6)
Limit
(Notes 7, 8)
I
DD
Quiescent Power Supply Current
V
DD
= 3.2V, V
IN
= 0, R
LOAD
=
14
27
mA (max)
I
SD
Shutdown Current
V
SHUTDOWN
= GND (Notes 9, 10)
0.1
2
A (max)
V
SDIH
Shutdown Voltage Input High
S/D1 and S/D2
1.5
V (min)
V
SDIL
Shutdown Voltage Input Low
S/D1 and S/D2
0.4
V (max)
T
WU
Wake-up Time
C
B
= 1.0F
80
110
msec
(max)
V
OS
Output Offset Voltage
5
40
mV (max)
TSD
Thermal Shutdown Temperature
125
C (min))
P
OUT
Output Power
THD = 2% (max), f = 1kHz,
Mono BTL
1
0.85
W (min)
THD+N
Total Harmomic Distortion + Noise
P
O
= 500mW, f
IN
= 1kHz
0.25
0.55
% (max)
e
OS
Output Noise
A-Weighted Filter, V
IN
= 0V
105
V
PSRR
Power Supply Rejection Ratio
V
RIPPLE
= 200mV
p-p
, f = 100Hz
66
dB (min)
LM4805
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3
Electrical Characteristics V
DD
= 3.0V
(Notes 1, 2) (Continued)
The following specifications apply for V
DD
= 3.0V, A
V-BTL
= 26dB, R
L
= 8
, C
B
= 1.0F, R
1
= 51.1k
, R
2
= 15k
unless other-
wise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4805
Units
(Limits)
Typical
(Note 6)
Limit
(Notes 7, 8)
V
FB
Feedback Pin Reference Voltage
(Note 11)
1.23
1.205
1.255
V (max)
V (min)
Note 1: All voltages are measured with respect to the GND 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 given in Absolute Maximum Ratings, whichever is lower.
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: Shutdown current is measured at an ambient temperature of 25C. The Shutdown pin should be driven as close as possible to GND for minimum shutdown
current.
Note 10: Shutdown current is measured with components R1 and R2 removed.
Note 11: Feedback pin reference voltage is measured with the Audio Amplifier's V1 (pin 26) floating and no addition load connected to the cathode of D1 (see Figure
1).
LM4805
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4
Typical Performance Characteristics
THD+N vs Frequency
V
DD
= 3V, A
V
= 6dB, R
L
= 8
THD+N vs Frequency
V
DD
= 3V, A
V
= 6dB, R
L
= 16
20126211
20126212
THD+N vs Frequency
V
DD
= 3V, A
V
= 26dB, R
L
= 8
THD+N vs Frequency
V
DD
= 3V, A
V
= 26dB, R
L
= 16
20126213
20126214
THD+N vs Frequency
V
DD
= 4.2V, A
V
= 6dB, R
L
= 8
THD+N vs Frequency
V
DD
= 4.2V, A
V
= 6dB, R
L
= 16
20126215
20126216
LM4805
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