LM4873
Dual 2.1W Audio Amplifier Plus Stereo Headphone
Function
General Description
The LM4873 is a dual bridge-connected audio power ampli-
fier which, when connected to a 5V supply, will deliver 2.1W
to a 4
load (Note 1) or 2.4W to a 3
load (Note 2)with less
than 1.0% THD+N. In addition, the headphone input pin al-
lows the amplifiers to operate in single-ended mode to drive
stereo headphones. A Mux Control pin toggles between the
two stereo sets of amplifier inputs, allowing for two select-
able amplifier closed-loop responses.
Boomer audio power amplifiers were designed specifically to
provide high quality output power from a surface mount
package while requiring few external components. To sim-
plify audio system design, the LM4873 combines dual bridge
speaker amplifiers and stereo headphone amplifiers on one
chip.
The LM4873 features an externally controlled, low-power
consumption shutdown mode, a stereo headphone amplifier
mode, and thermal shutdown protection. It also utilizes cir-
cuitry to reduce "clicks and pops" during device turn-on.
Note 1: An LM4873MTE-1 which has been properly mounted to the circuit
board will deliver 2.1W into 4
. The other package options for the LM4873
will deliver 1.1W into 8
. See the Application Information section for
LM4873MTE-1 usage information.
Note 2: An LM4873MTE-1 which has been properly mounted to the circuit
board and forced-air cooled will deliver 2.4W into 3
.
Key Specifications
n
P
O
at 1% THD+N
into 3
(LM4873MTE-1)
2.4W(typ)
into 4
(LM4873MTE-1)
2.1W(typ)
into 4
(LM4873MTE)
1.9W(typ)
into 8
(LM4873)
1.1W(typ)
n
Single-ended mode - THD+N
at 75mW into 32
0.5%(max)
n
Shutdown current
0.7A(typ)
Features
n
Input mux control and two separate inputs per channel
n
Stereo headphone amplifier mode
n
"Click and pop" suppression circuitry
n
Thermal shutdown protection circuitry
n
Exposed-DAP TSSOP and TSSOP packaging available
Applications
n
Multimedia monitors
n
Portable and desktop computers
n
Portable audio systems
Typical Application
Boomer
is a registered trademark of National Semiconductor Corporation.
DS100993-31
*
Refer to the section Proper Selection of External Components, for a detailed discussion of C
B
size.
FIGURE 1. Typical Audio Amplifier Application Circuit
April 2000
LM4873
Dual
2.1W
Audio
Amplifier
Plus
Stereo
Headphone
Function
2000 National Semiconductor Corporation
DS100993
www.national.com
Connection Diagram
Connection Diagram
DS100993-30
Top View
Order Number LM4873MTE-1
See NS Package Number MXA28A for Exposed-DAP TSSOP
DS100993-2
Top View
Order Number LM4873MT, LM4873MTE
See NS Package Number MTC20 for TSSOP
See NS Package Number MXA20A for Exposed-DAP TSSOP
LM4873
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2
Absolute Maximum Ratings
(Note 4)
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 14)
Internally limited
ESD Susceptibility (Note 15)
2000V
ESD Susceptibility (Note 16)
200V
Junction Temperature
150C
Solder Information
Small Outline Package
Vapor Phase (60 sec.)
215C
Infrared (15 sec.)
220C
See AN-450 "Surface Mounting and their Effects on
Product Reliablilty" for other methods of soldering surface
mount devices.
Thermal Resistance
JC
(typ) -- M16B
20C/W
JA
(typ) -- M16B
80C/W
JC
(typ) -- N16A
20C/W
JA
(typ) -- N16A
63C/W
JC
(typ) -- MTC20
20C/W
JA
(typ) -- MTC20
80C/W
JC
(typ) -- MXA20A
2C/W
JA
(typ) -- MXA20A
41C/W (Note 5)
JA
(typ) -- MXA20A
51C/W (Note 6)
JA
(typ) -- MXA20A
90C/W (Note 7)
JC
(typ) -- MXA28A
2C/W
JA
(typ) -- MXA28A
41C/W (Note 8)
JA
(typ) -- MXA28A
51C/W (Note 9)
JA
(typ) -- MXA28A
90C/W (Note 10)
Operating Ratings
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
85C
Supply Voltage
2.0V
V
DD
5.5V
Electrical Characteristics for Entire IC
(Notes 3, 4)
The following specifications apply for V
DD
= 5V unless otherwise noted. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4873
Units
(Limits)
Typical
Limit
(Note 17)
(Note 18)
V
DD
Supply Voltage
2
V (min)
5.5
V (max)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, I
O
= 0A (Note 19) , HP-IN = 0V
7.5
15
mA (max)
V
IN
= 0V, I
O
= 0A (Note 19) , HP-IN = 4V
5.8
6
mA (min)
I
SD
Shutdown Current
V
PIN1
= V
DD
0.7
2
A (min)
V
IH
Headphone High Input Voltage
4
V (min)
V
IL
Headphone Low Input Voltage
0.8
V (max)
Electrical Characteristics for Bridged-Mode Operation
(Notes 3, 4)
The following specifications apply for V
DD
= 5V unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4873
Units
(Limits)
Typical
Limit
(Note
17)
(Note
18)
V
OS
Output Offset Voltage
V
IN
= 0V
5
50
mV (max)
P
O
Output Power (Note 13)
THD = 1%, f = 1 kHz
LM4873MTE-1, R
L
= 3
(Note 11)
2.4
W
LM4873MTE, R
L
= 3
(Note 11)
2.2
W
LM4873MTE-1, R
L
= 4
(Note 12)
2.1
W
LM4873MTE, R
L
= 4
(Note 12)
1.9
W
LM4873, R
L
= 8
1.1
1.0
W (min)
THD+N = 10%, f = 1 kHz
LM4873MTE-1, R
L
= 3
(Note 11)
3.0
W
LM4873MTE-1, R
L
= 4
(Note 12)
2.6
LM4873, R
L
= 8
1.5
W
THD+N = 1%, f = 1 kHz, R
L
= 32
0.34
W
LM4873
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3
Electrical Characteristics for Bridged-Mode Operation
(Notes 3, 4) (Continued)
The following specifications apply for V
DD
= 5V unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4873
Units
(Limits)
Typical
Limit
(Note
17)
(Note
18)
THD+N
Total Harmonic Distortion+Noise
20 Hz
f
20 kHz, A
VD
= 2
LM4873MTE-1, R
L
= 4
, P
O
= 2W
0.3
LM4873, R
L
= 8
, P
O
= 1W
0.3
%
PSRR
Power Supply Rejection Ratio
V
DD
= 5V, V
RIPPLE
= 200 mV
RMS
, R
L
= 8
,
C
B
= 1.0 F
67
dB
X
TALK
Channel Separation
f = 1 kHz, C
B
= 1.0 F
80
dB
SNR
Signal To Noise Ratio
V
DD
= 5V, P
O
= 1.1W, R
L
= 8
97
dB
Electrical Characteristics for Single-Ended Operation
(Notes 3, 4)
The following specifications apply for V
DD
= 5V unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4873
Units
(Limits)
Typical
Limit
(Note
17)
(Note
18)
V
OS
Output Offset Voltage
V
IN
= 0V
5
50
mV (max)
P
O
Output Power
THD = 0.5%, f = 1 kHz, R
L
= 32
85
75
mW (min)
THD+N = 1%, f = 1 kHz, R
L
= 8
340
mW
THD+N = 10%, f = 1 kHz, R
L
= 8
440
mW
THD+N
Total Harmonic Distortion+Noise
A
V
= -1, P
O
= 75 mW, 20 Hz
f
20 kHz,
R
L
= 32
0.2
%
PSRR
Power Supply Rejection Ratio
C
B
= 1.0 F, V
RIPPLE
= 200 mV
RMS
,
f = 1 kHz
52
dB
X
TALK
Channel Separation
f = 1 kHz, C
B
= 1.0 F
60
dB
SNR
Signal To Noise Ratio
V
DD
= 5V, P
O
= 340mW, R
L
= 8
94
dB
Note 3: All voltages are measured with respect to the ground pins, 2, 7, and 15, unless otherwise specified.
Note 4: 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 5: The
JA
given is for an MXA20A package whose exposed-DAP is soldered to an exposed 2in
2
piece of 1 ounce printed circuit board copper.
Note 6: The
JA
given is for an MXA20A package whose exposed-DAP is soldered to an exposed 1in
2
piece of 1 ounce printed circuit board copper.
Note 7: The
JA
given is for an MXA20A package whose exposed-DAP is not soldered to any copper.
Note 8: The
JA
given is for an MXA28A package whose exposed-DAP is soldered to an exposed 2in
2
piece of 1 ounce printed circuit board copper.
Note 9: The
JA
given is for an MXA28A package whose exposed-DAP is soldered to an exposed 1in
2
piece of 1 ounce printed circuit board copper.
Note 10: The
JA
given is for an MXA28A package whose exposed-DAP is not soldered to any copper.
Note 11: When driving 3
loads from a 5V supply, the LM4873MTE or LM4873MTE-1 must be mounted to the circuit board and forced-air cooled (450 linear-feet
per minute).
Note 12: When driving 4
loads from a 5V supply, the LM4873MTE or LM4873MTE-1 must be mounted to the circuit board.
Note 13: Output power is measured at the device terminals.
Note 14: 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 LM4873, T
JMAX
= 150C. For the
JA
s for different packages, please see the Application Informa-
tion section or the Absolute Maximum Ratings section.
Note 15: Human body model, 100 pF discharged through a 1.5 k
resistor.
Note 16: Machine model, 220 pF240 pF discharged through all pins.
Note 17: Typicals are measured at 25C and represent the parametric norm.
Note 18: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
Note 19: The quiescent power supply current depends on the offset voltage when a practical load is connected to the amplifier.
LM4873
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4
Truth Table for Logic Inputs
SHUTDOWN
HP-IN
INPUT
SELECT
LM4873 MODE (INPUT #)
Low
Low
Low
Bridged (1)
Low
Low
High
Bridged (2)
Low
High
Low
Single-Ended (1)
Low
High
High
Single-Ended (2)
High
X
X
Shutdown
LM4873
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