LM4850
Mono 1.5 W / Stereo 300 mW Power Amplifier
General Description
The LM4850 is an audio power amplifier capable of deliver-
ing 1.5W (typ) of continuous average power into a mono 4
bridged-tied load (BTL) with 1% THD+N or 95mW per chan-
nel
of
continuous
average
power
into
stereo
32
single-ended (SE) loads with 1% THD+N, using a 5V power
supply.
The LM4850 can automatically switch between mono BTL
and stereo SE modes utilizing a headphone sense pin. It is
ideal for any system that provides both a monaural speaker
output and a stereo line or headphone output
Boomer audio power amplifiers were designed specifically to
provide high quality output power with a minimal amount of
external components. Since the LM4850 does not require
bootstrap capacitors or snubber networks, it is optimally
suited for low-power portable systems.
The LM4850 features an externally controlled, micropower
consumption shutdown mode and thermal shutdown protec-
tion. The unity-gain stable LM4850's gain is set by external
gain-setting resistors
Note 1: An LM4850LD that has been properly mounted to a circuit board will
deliver 1.9W into 3
(at 1% THD+N). The other package options for the
LM4850 will deliver 1.1W into 8
(at 1% THD+N). See Application Infor-
mation sections for further information concerning the LM4850LD,
LM4850MM, and LM4850MT.
Key Specifications
n
Output Power at 1% THD+N, 1kHz:
n
LM4850LD 3
BTL
1.9W (typ)
n
LM4850LD 4
BTL
1.7W (typ)
n
LM4850MM, MT 4
BTL
1.5W (typ)
n
LM4850LD, MM, MT 8
BTL
1.1W (typ)
n
LM4850LD, MM, MT 8
SE
300mW (typ)
n
LM4850LD, MM, MT 32
SE
95mW (typ)
n
THD+N at 1kHz, 95mW into 32
SE
1% (typ)
n
Single Supply Operation
2.4 to 5.5V
n
Shutdown Current
44A (typ)
Features
n
Mono 1.5W BTL or stereo 300mW output
n
Headphone sense
n
"Click and pop" suppression circuitry
n
No bootstrap capacitors required
n
Thermal shutdown protection
n
Unity-gain stable
n
LLP, TSSOP, and MSOP packaging
Applications
n
Portable computers
n
Desktop computers
n
PDA's
n
Handheld games
Typical Application
Boomer
is a registered trademark of National Semiconductor Corporation.
20001031
FIGURE 1. Typical Audio Amplifier Application Circuit
July 2002
LM4850
Mono
1.
5
W
/
Stereo
300
mW
Power
Amplifier
2002 National Semiconductor Corporation
DS200010
www.national.com
Connection Diagrams
20001051
Top View
10 Lead MSOP
Order Number LM4850MM
See NS Package Number MUB10A
20001052
Top View
14 Lead TSSOP
Order Number LM4850MT
See NS Package Number MTC14
20001002
Top View
14 Lead LLP
Order Number LM4850LD
See NS Package Number LDA14A
LM4850
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2
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
ESD Susceptibility (Note 5)
3.5kV
ESD Machine model (Note 8)
250V
Junction Temperature (T
J
)
150C
Solder Information (Note 2)
Small Outline Package
Vapor Phase (60 sec.)
215C
Infrared (15 sec.)
220C
Thermal Resistance
JA
(typ) -- MUB10A
194C/W
JC
(typ) -- MUB10A
52C/W
JA
(typ) -- MTC14
150C/W
JC
(typ) -- MTC14
40C/W
JA
(typ) -- LDA14A (Note 10)
56C/W
JC
(typ) -- LDA14A
4.3C/W
Operating Ratings
(Note 3)
Temperature Range
-40C
to 85C
Supply Voltage V
DD
2.4V
V
DD
5.5V
Note 2: See AN-450 'Surface Mounting and their effects on Product Reliabil-
ity' for other methods of soldering surface mount devices.
Electrical Characteristics
(Notes 3, 9)
The following specifications apply for V
DD
= 5.0V, T
A
= 25C unless otherwise specified.
Symbol
Parameter
Conditions
LM4850
Units
(Limits)
Typical
(Note 6)
Limit
(Note 7)
V
DD
Supply Voltage
2.4
V (min)
5.5
V (max)
I
DD
Supply Current
BTL Mode; V
IN
= 0V; I
O
= 0A
2.4
7.0
mA
SE Mode; V
IN
= 0V; I
O
= 0A
2.4
7.0
mA
I
SD
Shutdown Current
SD Mode
44
A
V
OS
Output Offset Voltage
BTL Mode; A
V
= 2
BTL OUT+ to BTL OUT-
5.0
40
mV
P
O
Output Power
LM4850LD; BTL Mode; R
L
= 3
THD+N = 1% (Note 11)
1.9
W
LM4850LD; BTL Mode; R
L
= 4
THD+N = 1% (Note 11)
1.7
W
LM4850MT, MM; BTL Mode; R
L
= 4
THD+N = 1%
1.5
W
BTL Mode; R
L
= 8
THD+N = 1%
1.1
W
SE Mode; R
L
= 8
THD+N = 1%
300
mW
SE Mode; R
L
= 32
THD+N = 1%
95
mW
V
IH
Shutdown Input Voltage High
Is
<
80A
2.0
V (min)
V
IL
Shutdown Input Voltage Low
Is
>
0.5mA
0.8
V (max)
Crosstalk Channel Seperation
SE Mode, R
L
= 32
; f = 1kHz
73
dB
Electrical Characteristics
(Notes 3, 9)
The following specifications apply for V
DD
= 3.3V, T
A
= 25C unless otherwise specified.
Symbol
Parameter
Conditions
LM4850
Units
(Limits)
Typical
(Note 6)
Limit
(Note 7)
I
DD
Supply Current
BTL Mode; V
IN
= 0V; I
O
= 0A
2.0
mA
LM4850
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3
Electrical Characteristics
(Notes 3, 9) (Continued)
The following specifications apply for V
DD
= 3.3V, T
A
= 25C unless otherwise specified.
Symbol
Parameter
Conditions
LM4850
Units
(Limits)
Typical
(Note 6)
Limit
(Note 7)
SE Mode; V
IN
= 0V; I
O
= 0A
2.0
mA
I
SD
Shutdown Current
SD Mode
30
A
V
OS
Output Offset Voltage
BTL Mode; A
V
= 2
BTL OUT+ to BTL OUT-
5.0
40
mV
P
O
Output Power
BTL Mode; R
L
= 8
THD+N = 1%
440
mW
SE Mode; R
L
= 32
THD+N = 1%
40
mW
V
IH
Shutdown Input Voltage High
Is
<
80A
2.0
V (min)
V
IL
Shutdown Input Voltage Low
Is
>
0.5mA
0.8
V (max)
Electrical Characteristics
(Notes 3, 9)
The following specifications apply for V
DD
= 2.7V, T
A
= 25C unless otherwise specified.
Symbol
Parameter
Conditions
LM4850
Units
(Limits)
Typical
(Note 6)
Limit
(Note 7)
I
DD
Supply Current
BTL Mode; V
IN
= 0V; I
O
= 0A
1.8
mA
SE Mode; V
IN
= 0V; I
O
= 0A
1.8
mA
I
SD
Shutdown Current
SD Mode
25
A
V
OS
Output Offset Voltage
BTL Mode; A
V
= 2
BTL OUT+ to BTL OUT-
5.0
40
mV
P
O
Output Power
BTL Mode; R
L
= 8
THD+N = 1%
300
mW
SE Mode; R
L
= 32
THD+N = 1%
25
mW
V
IH
Shutdown Input Voltage High
Is
<
80 A
2.0
V (min)
V
IL
Shutdown Input Voltage Low
Is
>
0.5mA
0.8
V (max)
Note 3: Absolute Maximum Rating indicate limits beyond which damage to the device may occur.
Note 4: Operating Ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits. For guaranteed specifications and
test conditions, see the Electrical Characteristics. The guaranteed specifications apply only for the test conditions listed. Some performance characteristics may
degrade when the device is not operated under the listed test conditions.
Note 5: Human body model, 100pF discharged through a 1.5k
resistor.
Note 6: Typical specifications are specified at +25C and represent the most likely parametric norm.
Note 7: Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis.
Note 8: Machine Model ESD test is covered by specification EIAJ IC-121-1981. A 200pF cap is charged to the specified voltage, then discharged directly into the
IC with no external series resistor (resistance of discharge path must be under 50
).
Note 9: All voltages are measured with respect to the ground pin, unless otherwise specified.
Note 10: The given
JA
is for a LM4850LD with the Exposed-DAP soldered to an exposed 1in
2
area of 1oz printed circuit board copper.
Note 11: When driving 3
or 4 loads from a 5V supply, the LM4850 must be mounted to a circuit board.
Note 12: Limits are guaranteed to National's AOQL ( Average Outgoing Quality Level ).
External Components Description
(Refer to 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
).
LM4850
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4
External Components Description
(Continued)
(Refer to Figure 1.)
Components
Functional Description
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 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
.
6.
C
O
Output coupling capacitor which blocks the DC voltage at the amplifier's output. Forms a high pass filter
with the single-ended load R
L
at f
O
= 1/(2
R
L
C
O
).
Typical Performance Characteristics
LD Specific Characteristics
LM4850LD
THD+N vs Frequency
LM4850LD
THD+N vs Frequency
20001075
20001076
LM4850LD
THD+N vs Output Power
LM4850LD
THD+N vs Output Power
20001077
20001078
LM4850
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