LM4881
Dual 200 mW Headphone Amplifier with Shutdown Mode
General Description
The LM4881 is a dual audio power amplifier capable of deliv-
ering 200 mW of continuous average power into an 8
load
with 0.1% (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 using surface mount packaging. Since
the LM4881 does not require bootstrap capacitors or snub-
ber networks, it is optimally suited for low-power portable
systems.
The LM4881 features an externally controlled, low power
consumption shutdown mode which is virtually clickless and
popless, as well as an internal thermal shutdown protection
mechanism.
The unity-gain stable LM4881 can be configured by external
gain-setting resistors.
Key Specifications
n
THD at 1 kHz at 125 mW
continuous average output
power into 8
0.1% (max)
n
THD at 1 kHz at 75 mW continuous
average output power into 32
0.02% (typ)
n
Output power at 10% THD+N
at 1 kHz into 8
300 mW (typ)
n
Shutdown Current
0.7 A (typ)
Features
n
MSOP surface mount packaging
n
Unity-gain stable
n
External gain configuration capability
n
Thermal shutdown protection circuitry
n
No bootstrap capacitors, or snubber circuits are
necessary
Applications
n
Headphone Amplifier
n
Personal Computers
n
Microphone Preamplifier
Typical Application
Connection Diagrams
Boomer
is a registered trademark of National Semiconductor Corporation.
DS100005-1
*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
MSOP Package
DS100005-2
SOP and DIP Package
DS100005-38
Top View
Order Number LM4881MM, LM4881M, or LM4881N
See NS Package Number MUA08A, M08A, or N08E
September 1997
LM4881
Dual
200
mW
Headphone
Amplifier
with
Shutdown
Mode
1999 National Semiconductor Corporation
DS100005
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
JC
(DIP)
37C/W
JA
(DIP)
107C/W
Operating Ratings
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
85C
Supply Voltage
2.7V
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 for T
A
= 25C.
Symbol
Parameter
Conditions
LM4881
Units (Limits)
Typ (Note 7)
Limit (Note 8)
V
DD
Power Supply Voltage
2.7
V (min)
5.5
V (max)
I
DD
Quiescent Current
V
IN
= 0V, I
O
= 0A
3.6
6.0
mA (max)
I
SD
Shutdown Current
V
PIN1
= V
DD
0.7
5
A (max)
V
OS
Offset Voltage
V
IN
= 0V
5
50
mV (max)
P
O
Output Power
THD = 0.1% (max); f = 1 kHz;
R
L
= 8
200
125
mW (min)
R
L
= 16
150
mW
R
L
= 32
85
mW
THD + N = 10%; f = 1 kHz;
R
L
= 8
300
mW
R
L
= 16
200
mW
R
L
= 32
110
mW
THD+N
Total Harmonic Distortion +
Noise
R
L
= 16
, P
O
= 120 mWrms;
0.025
%
R
L
= 32
, P
O
= 75 mWrms;
f = 1 kHz
0.02
%
PSRR
C
B
= 1.0 F, V
RIPPLE
= 200
mVrms, f = 120Hz
50
dB
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2
Electrical Characteristics
(Notes 2, 3)
The following specifications apply for V
DD
= 3V unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4881
Units (Limits)
Typ (Note 7)
Limit (Note 8)
I
DD
Quiescent Current
V
IN
= 0V, I
O
= 0A
1.1
mA
I
SD
Shutdown Current
V
PIN1
= V
DD
0.7
A
V
OS
Offset Voltage
V
IN
= 0V
5
mV
P
O
Output Power
THD = 1% (max);
f = 1 kHz;
R
L
= 8
70
mW
R
L
= 16
65
mW
R
L
= 32
30
mW
THD + N = 10%;
f = 1 kHz;
R
L
= 8
95
mW
R
L
= 16
65
mW
R
L
= 32
35
mW
THD+N
Total Harmonic Distortion +
Noise
R
L
= 16
, P
O
= 60 mWrms;
0.2
%
R
L
= 32
, P
O
=
25 mWrms; f = 1 kHz
0.03
%
PSRR
Power Supply Rejection Ratio
C
B
= 1.0 F, V
RIPPLE
=
200 mVrms, f = 100 Hz
50
dB
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 LM4881, 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).
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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
)
Typical Performance Characteristics
THD+N vs Frequency
DS100005-3
THD+N vs Frequency
DS100005-4
THD+N vs Frequency
DS100005-5
THD+N vs Frequency
DS100005-6
THD+N vs Frequency
DS100005-7
THD+N vs Frequency
DS100005-8
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4
Typical Performance Characteristics
(Continued)
THD+N vs Output Power
DS100005-9
THD+N vs Output Power
DS100005-10
THD+N vs Output Power
DS100005-11
THD+N vs Output Power
DS100005-12
THD+N vs Output Power
DS100005-13
THD+N vs Output Power
DS100005-14
Output Power vs
Supply Voltage
DS100005-15
Output Power vs
Supply Voltage
DS100005-16
Output Power vs
Supply Voltage
DS100005-17
www.national.com
5
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