LM4808
Dual 105 mW Headphone Amplifier
General Description
The LM4808 is a dual audio power amplifier capable of deliv-
ering 105 mW per channel of continuous average power into
a 16
load with 0.1% (THD+N) 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 using surface mount packaging. Since
the LM4808 does not require bootstrap capacitors or snub-
ber networks, it is optimally suited for low-power portable
systems.
The unity-gain stable LM4808 can be configured by external
gain-setting resistors.
Key Specifications
n
THD+N at 1 kHz at 105 mW
continuous average output
power into 16
0.1% (max)
n
THD+N at 1 kHz at 70 mW
continuous average output
power into 32
0.1% (typ)
n
Output power at 0.1% THD+N
at 1 kHz into 32
70 mW (typ)
Features
n
SOP and MSOP surface mount packaging
n
Switch on/off click suppression
n
Excellent power supply ripple rejection
n
Unity-gain stable
n
Minimum external components
Applications
n
Headphone Amplifier
n
Personal Computers
n
Microphone Preamplifier
Typical Application
Connection Diagram
Boomer
is a registered trademark of National Semiconductor Corporation.
DS101276-1
*Refer to the Application Information Section for information concerning
proper selection of the input and output coupling capacitors.
FIGURE 1. Typical Audio Amplifier Application Circuit
SOP & MSOP Package
DS101276-2
Top View
Order Number LM4808M, LM4808MM
See NS Package Number M08A, MUA08A
February 2000
LM4808
Dual
105
mW
Headphone
Amplifier
2000 National Semiconductor Corporation
DS101276
www.national.com
Absolute Maximum Ratings
(Note 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 (Note 4)
Internally limited
ESD Susceptibility (Note 5)
3500V
ESD Susceptibility (Note 6)
250V
Junction Temperature
150C
Soldering Information (Note 1)
Small Outline Package
Vapor Phase (60 seconds)
215C
Infrared (15 seconds)
220C
Thermal Resistance
JC
(MSOP)
56C/W
JA
(MSOP)
210C/W
JC
(SOP)
35C/W
JA
(SOP)
170C/W
Operating Ratings
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
85C
Supply Voltage
2.0V
V
DD
5.5V
Note 1: See AN-450 "Surface Mounting and their Effects on Product Reli-
ability" for other methods of soldering surface mount devices.
Electrical Characteristics
(Notes 2, 3)
The following specifications apply for V
DD
= 5V unless otherwise specified, limits apply to T
A
= 25C.
Symbol
Parameter
Conditions
LM4808
Units (Limits)
Typ (Note 7)
Limit (Note 8)
V
DD
Supply Voltage
2.0
V (min)
5.5
V (max)
I
DD
Supply Current
V
IN
= 0V, I
O
= 0A
1.2
3.0
mA (max)
P
tot
Total Power Dissipation
V
IN
= 0V, I
O
= 0A
6
16.5
mW (max)
V
OS
Input Offset Voltage
V
IN
= 0V
10
50
mV (max)
Ibias
Input Bias Current
10
pA
V
CM
Common Mode Voltage
0
V
4.3
V
G
V
Open-Loop Voltage Gain
R
L
= 5k
67
dB
Io
Max Output Current
THD+N
<
0.1 %
70
mA
R
O
Output Resistance
0.1
V
O
Output Swing
R
L
= 32
, 0.1% THD+N, Min
.3
V
R
L
= 32
, 0.1% THD+N, Max
4.7
PSRR
Power Supply Rejection Ratio
Cb = 1.0F, Vripple = 100mV
PP
,
f = 100Hz
89
dB
Crosstalk
Channel Separation
R
L
= 32
75
dB
THD+N
Total Harmonic Distortion +
Noise
f = 1 kHz
R
L
= 16
,
V
O
=3.5V
PP
(at 0 dB)
0.05
%
66
dB
R
L
= 32
,
V
O
=3.5V
PP
(at 0 dB)
0.05
%
66
dB
SNR
Signal-to-Noise Ratio
V
O
= 3.5V
pp
(at 0 dB)
105
dB
f
G
Unity Gain Frequency
Open Loop, R
L
= 5k
5.5
MHz
P
o
Output Power
THD+N = 0.1%, f = 1 kHz
R
L
= 16
105
mW
R
L
= 32
70
60
mW
THD+N = 10%, f = 1 kHz
R
L
= 16
150
mW
R
L
= 32
90
mW
C
I
Input Capacitance
3
pF
C
L
Load Capacitance
200
pF
SR
Slew Rate
Unity Gain Inverting
3
V/s
LM4808
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2
Electrical Characteristics
(Notes 2, 3)
The following specifications apply for V
DD
= 3.3V unless otherwise specified, limits apply to T
A
= 25C.
Symbol
Parameter
Conditions
Conditions
Units (Limits)
Typ (Note 7)
Limit (Note 8)
I
DD
Supply Current
V
IN
= 0V, I
O
= 0A
1.0
mA (max)
V
OS
Input Offset Voltage
V
IN
= 0V
7
mV (max)
P
o
Output Power
THD+N = 0.1%, f = 1 kHz
R
L
= 16
40
mW
R
L
= 32
28
mW
THD+N = 10%, f = 1 kHz
R
L
= 16
56
mW
R
L
= 32
38
mW
Electrical Characteristics
(Notes 2, 3)
The following specifications apply for V
DD
= 2.6V unless otherwise specified, limits apply to T
A
= 25C.
Symbol
Parameter
Conditions
Conditions
Units (Limits)
Typ (Note 7)
Limit (Note 8)
I
DD
Supply Current
V
IN
= 0V, I
O
= 0A
0.9
mA (max)
V
OS
Input Offset Voltage
V
IN
= 0V
5
mV (max)
P
o
Output Power
THD+N = 0.1%, f = 1 kHz
R
L
= 16
20
mW
R
L
= 32
16
mW
THD+N = 10%, f = 1 kHz
R
L
= 16
31
mW
R
L
= 32
22
mW
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 func-
tional, but do not guarantee specific performance limits.
Electrical Characteristics
state DC and AC electrical specifications under particular test conditions which guar-
antee 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 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 LM4808, T
JMAX
= 150C, and the typical junction-to-ambient thermal resistance, when board
mounted, is 210C/W for the MSOP Package and 107C/W for package N08E.
Note 5: Human body model, 100 pF discharged through a 1.5 k
resistor.
Note 6: Machine Model, 220 pF240 pF discharged through all pins.
Note 7: Typicals are measured at 25C and represent the parametric norm.
Note 8: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
LM4808
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3
External Components Description
(
Figure 1)
Compo-
nents
Functional Description
1. R
i
Inverting input resistance which sets the closed-loop gain in conjuction 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 amplifier's 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 and explanation of how to determine the value of C
i
.
3. R
f
Feedback resistance which sets closed-loop gain in conjuction with R
i
.
4. C
S
Supply bypass capacitor which provides power supply filtering. Refer to the Application Information
section for 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
.
6. C
O
Output coupling capacitor which blocks the DC voltage at the amplifier's output. Forms a high pass
filter with R
L
at f
O
= 1/(2
R
L
C
O
)
7. R
B
Resistor which forms a voltage divider that provides a half-supply DC voltage to the non-inverting
input of the amplifier.
Typical Performance Characteristics
THD+N vs Frequency
DS101276-3
THD+N vs Frequency
DS101276-4
THD+N vs Frequency
DS101276-5
THD+N vs Frequency
DS101276-6
THD+N vs Frequency
DS101276-7
THD+N vs Frequency
DS101276-8
LM4808
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Typical Performance Characteristics
(Continued)
THD+N vs Frequency
DS101276-9
THD+N vs Frequency
DS101276-10
THD+N vs Frequency
DS101276-11
THD+N vs Frequency
DS101276-12
THD+N vs Output Power
DS101276-13
THD+N vs Output Power
DS101276-14
THD+N vs Output Power
DS101276-15
THD+N vs Output Power
DS101276-16
THD+N vs Output Power
DS101276-17
LM4808
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