LM4861
1.1W Audio Power Amplifier with Shutdown Mode
General Description
The LM4861 is a bridge-connected audio power amplifier
capable of delivering 1.1W of continuous average power to
an 8
load with 1% THD+N using 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 LM4861 does not require output coupling capacitors,
bootstrap capacitors, or snubber networks, it is optimally
suited for low-power portable systems.
The LM4861 features an externally controlled, low-power
consumption shutdown mode, as well as an internal thermal
shutdown protection mechanism.
The unity-gain stable LM4861 can be configured by external
gain-setting resistors for differential gains of up to 10 without
the use of external compensation components. Higher gains
may be achieved with suitable compensation.
Key Specifications
j
THD+N for 1kHz at 1W continuous
average output power into 8
1.0% (max)
j
Output power at 10% THD+N
at 1kHz into 8
1.5W (typ)
j
Shutdown Current
0.6A (typ)
Features
n
No output coupling capacitors, bootstrap capacitors, or
snubber circuits are necessary
n
Small Outline (SO) packaging
n
Compatible with PC power supplies
n
Thermal shutdown protection circuitry
n
Unity-gain stable
n
External gain configuration capability
Applications
n
Personal computers
n
Portable consumer products
n
Self-powered speakers
n
Toys and games
Connection Diagram
Small Outline Package
01198602
Top View
Order Number LM4861M
See NS Package Number M08A
Boomer
is a registered trademark of National Semiconductor Corporation.
February 2003
LM4861
1.1W
Audio
Power
Amplifier
with
Shutdown
Mode
2003 National Semiconductor Corporation
DS011986
www.national.com
Typical Application
01198601
FIGURE 1. Typical Audio Amplifier Application Circuit
LM4861
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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)
3000V
ESD Susceptibility (Note 5)
250V
Junction Temperature
150C
Soldering Information
Small Outline Package
Vapor Phase (60 sec.)
Infrared (15 sec.)
215C
220C
See AN-450 "Surface Mounting and their Effects on
Product Reliability" for other methods of soldering surface
mount devices.
Operating Ratings
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
+85C
Supply Voltage
2.0V
V
DD
5.5V
Thermal Resistance
JC
(typ) -- M08A
35C/W
JA
(typ) -- M08A
140C/W
JC
(typ) -- N08E
37C/W
JA
(typ) -- N08E
107C/W
Electrical Characteristics
(Note 1) (Note 2)
The following specifications apply for V
DD
= 5V, unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4861
Units
(Limits)
Typical
Limit
(Note 6)
(Note 7)
V
DD
Supply Voltage
2.0
V (min)
5.5
V (max)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, I
O
= 0A (Note 8)
6.5
10.0
mA (max)
I
SD
Shutdown Current
V
pin1
= V
DD
0.6
10.0
A (max)
V
OS
Output Offset Voltage
V
IN
= 0V
5.0
50.0
mV (max)
P
O
Output Power
THD = 1% (max); f = 1 kHz
1.1
1.0
W (min)
THD+N
Total Harmonic Distortion + Noise
P
O
= 1Wrms; 20 Hz
f 20 kHz
0.72
%
PSRR
Power Supply Rejection Ratio
V
DD
= 4.9V to 5.1V
65
dB
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 the Absolute Maximum Ratings, whichever is lower. For the LM4861, T
JMAX
= 150C,
and the typical junction-to-ambient thermal resistance, when board mounted, is 140C/W.
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 Nationai's AOQL (Average Outgoing Quality Level).
Note 8: The quiescent power supply current depends on the offset voltage when a practical load is connected to the amplifier.
LM4861
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3
High Gain Application Circuit
Single Ended Application Circuit
01198603
FIGURE 2. Audio Ampiifier with A
VD
= 20
01198604
*C
S
and C
B
size depend on specific application requirements and constraints. Typical vaiues of C
S
and C
B
are 0.1 F.
**Pin 1 should be connected to V
DD
to disable the amplifier or to GND to enable the amplifier. This pin should not be left floating.
***These components create a "dummy" load for pin 8 for stability purposes.
FIGURE 3. Single-Ended Amplifier with A
V
= -1
LM4861
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External Components Description
(Figures 1, 2)
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 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
).
3. R
f
Feedback resistance which sets closed-loop gain in conjunction 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 supply bypass capacitor.
5. C
B
Bypass pin capacitor which provides half supply filtering. Refer to the Application Information section
for
proper placement and selection of bypass capacitor.
6. C
f
(Note 9)
C
f
in conjunction with R
f
creates a low-pass filter which bandwidth limits the amplifier and prevents
possible
high frequency oscillation bursts.
f
C
= 1 / (2
R
f
C
f
)
Note 9: Optional component dependent upon specific design requirements. Refer to the Application Information section for more information.
Typical Performance Characteristics
THD+N vs Frequency
THD+N vs Frequency
01198605
01198606
THD+N vs Frequency
THD+N vs Output Power
01198607
01198609
LM4861
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