LM4868
Output-Transient-Free Dual 2.1W Audio Amplifier Plus
No Coupling Capacitor Stereo Headphone Function
General Description
The LM4868 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. The LM4868 uses advanced, latest gen-
eration circuitry to eliminate all traces of clicks and pops
when the supply voltage is first applied. The amplifier has a
headphone-amplifier-select input pin. It is used to switch the
amplifiers from bridge to single-ended mode for driving
headphones. A new circuit topology eliminates headphone
output coupling capacitors (patent pending). A MUX control
pin allows selection between the two sets of stereo input
signals. The MUX control can also be used to select be-
tween two different customer-specified closed-loop re-
sponses.
Boomer audio power amplifiers are designed specifically to
provide high quality output power from a surface mount
package and require few external components. To simplify
audio system design, the LM4868 combines dual bridge
speaker amplifiers and stereo headphone amplifiers in one
package.
The LM4868 features an externally controlled power-saving
micropower shutdown mode, a stereo headphone amplifier
mode, and thermal shutdown protection.
Note 1: An LM4868LQ or LM4868MTE that has been properly mounted to
a circuit board will deliver 2.1W into 4
. The Mux control can also be used to
select two different closed-loop responses. LM4868MT will deliver 1.1W into
8
. See the Application Information sections for further information concern-
ing the LM4868LQ and the LM4868MT.
Note 2: An LM4868LQ or LM4868MTE that has been properly mounted to a
circuit board and forced-air cooled will deliver 2.4W into 3
.
Key Specifications
n
P
O
at 1% THD+N
n
LM4868LQ, 3
load
2.4W (typ)
n
LM4868LQ, 4
load
2.1W (typ)
n
LM4868MTE, 4
1.9W (typ)
n
LM4868MT, 8
1.1W (typ)
n
Single-ended mode - THD+N at 75mW into 32
0.5%
(max)
n
Shutdown current
0.7A (typ)
Features
n
Advanced "click and pop" suppression circuitry
n
Eliminates headphone amplifier output coupling
capacitors (patent pending)
n
Stereo headphone amplifier mode
n
Input mux control and two separate inputs per channel
n
Thermal shutdown protection circuitry
n
LLP, TSSOP, and exposed-DAP TSSOP packaging
available
Applications
n
Multimedia monitors
n
Portable and desktop computers
n
Portable audio systems
Connection Diagrams
20026758
Top View
Order Number LM4868MT, LM4868MTE
See NS Package Number MTC20 for TSSOP
See NS Package Number MXA20A for Exposed-DAP TSSOP
Boomer
is a registered trademark of National Semiconductor Corporation.
August 2002
LM4868
Output-T
ransient-Free
Dual
2.1W
Audio
Amplifier
Plus
No
Coupling
Capacitor
Stereo
Headphone
Function
2002 National Semiconductor Corporation
DS200267
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)
All pins except Pin 3 (MT, MTE), Pin 2 (LQ)
2000V
Pin 3 (MT, MTE), Pin 2 (LQ)
8000V
ESD Susceptibility (Note 6)
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) -- MTC20
20C/W
JA
(typ) -- MTC20
80C/W
JC
(typ) -- MXA20A
2C/W
JA
(typ) -- MXA20A
41C/W (Note 7)
JA
(typ) -- MXA20A
51C/W (Note 8)
JA
(typ) -- MXA20A
90C/W (Note 9)
JC
(typ) -- LQA24A
3.0C/W
JA
(typ) -- LQA24A
42C/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, 11)
The following specifications apply for V
DD
= 5V unless otherwise noted. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4868
Units
(Limits)
Typical
Limit
(Note 12)
(Note 13)
V
DD
Supply Voltage
2
V (min)
5.5
V (max)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, I
O
= 0A (Note 14), HP-IN = 0V
7.5
15
mA (max)
V
IN
= 0V, I
O
= 0A (Note 14), HP-IN = 4V
3.0
6
mA (max)
I
SD
Shutdown Current
V
DD
applied to the SHUTDOWN pin
0.7
2
A (max)
TH
um
Un-Mute Threshold Voltage
GND applied to SHUTDOWN pin
V
IN
applied to selected MUX channel
25
10
40
mV (min)
mV (max)
Electrical Characteristics for Bridged-Mode Operation
(Notes 3, 11)
The following specifications apply for V
DD
= 5V unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4868
Units
(Limits)
Typical
Limit
(Note 12)
(Note 13)
V
OS
Output Offset Voltage
V
IN
= 0V
5
50
mV (max)
P
O
Output Power (Note 15)
THD = 1%, f = 1kHz
(Note 16)
LM4868MTE, R
L
= 3
2.2
W
LM4868LQ, R
L
= 3
2.4
W
LM4868MTE, R
L
= 4
1.9
W
LM4868LQ, R
L
= 4
2.1
W
LM4868, R
L
= 8
1.1
1.0
W (min)
THD+N = 10%, f = 1kHz (Note 16)
LM4868MTE, R
L
= 3
3.0
W
LM4868LQ, R
L
= 3
3.0
W
LM4868MTE, R
L
= 4
2.6
W
LM4868LQ, R
L
= 4
2.6
W
LM4868, R
L
= 8
1.5
W
THD+N = 1%, f = 1 kHz, R
L
= 32
0.34
W
LM4868
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3
Electrical Characteristics for Bridged-Mode Operation
(Notes 3, 11) (Continued)
The following specifications apply for V
DD
= 5V unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4868
Units
(Limits)
Typical
Limit
(Note 12)
(Note 13)
THD+N
Total Harmonic Distortion+Noise
20Hz
f 20kHz, A
VD
= 2
LM4868MTE, R
L
= 4
, P
O
= 2W
LM4868LQ, R
L
= 4
, P
O
= 2W
LM4868, R
L
= 8
, P
O
= 1W
0.3
0.3
0.3
%
%
%
PSRR
Power Supply Rejection Ratio
V
DD
= 5V, V
RIPPLE
= 200 mV
RMS
, R
L
= 8
,
C
B
= 2.2F
67
dB
X
TALK
Channel Separation
f = 1 kHz, C
B
= 2.2F
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, 11)
The following specifications apply for V
DD
= 5V unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4868
Units
(Limits)
Typical
Limit
(Note 12)
(Note 13)
V
OS
Output Offset Voltage
V
IN
= 0V
5
50
mV (max)
P
O
Output Power
THD = 0.5%, f = 1kHz, R
L
= 32
85
75
mW (min)
THD+N = 1%, f = 1kHz, R
L
= 8
(Note
17)
180
mW
THD+N = 1%, f = 1kHz, R
L
= 16
THD+N = 1%, f = 1kHz, R
L
= 32
THD+N = 10%, f = 1kHz, R
L
= 16
THD+N = 10%, f = 1kHz, R
L
= 32
165
88
208
114
mW
mW
mW
mW
V
OUT
Output Voltage Swing
THD = 0.05%, R
L
= 5k
1
V
P-P
THD+N
Total Harmonic Distortion+Noise
A
V
= -1, P
O
= 75mW, 20 Hz
f 20kHz,
R
L
= 32
0.2
%
PSRR
Power Supply Rejection Ratio
C
B
= 2.2F, V
RIPPLE
= 200mV
RMS
,
f = 1kHz
52
dB
X
TALK
Channel Separation
f = 1kHz, C
B
= 2.2F
60
dB
SNR
Signal To Noise Ratio
V
DD
= 5V, P
O
= 340mW, R
L
= 8
94
dB
Note 3: 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 operates within the Operating Ratings. Specifications are not guaranteed for parameters where
no limit is given. The typical value however, 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 LM4868, T
JMAX
= 150C. For the
JA
s for different packages, please see the Application
Information section or the Absolute Maximum Ratings section.
Note 5: Human body model, 100pF discharged through a 1.5k
resistor.
Note 6: Machine model, 220pF240pF discharged through all pins.
Note 7: The given
JA
is for an LM4868 packaged in an MXA20A with the Exposed-DAP soldered to an exposed 2in
2
area of 1oz printed circuit board copper.
Note 8: The given
JA
is for an LM4868 packaged in an MXA20A with the Exposed-DAP soldered to an exposed 1in
2
area of 1oz printed circuit board copper.
Note 9: The given
JA
is for an LM4868 packaged in an MXA20A with the Exposed-DAP not soldered to printed circuit board copper.
Note 10: The given
JA
is for an LM4868 packaged in an LQA24A with the Exposed-DAP soldered to an exposed 2in
2
area of 1oz printed circuit board copper.
Note 11: All voltages are measured with respect to the ground (GND) pins, unless otherwise specified.
Note 12: Typicals are measured at 25C and represent the parametric norm.
Note 13: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level). Datasheet min/max specification limits are guaranteed by design, test, or
statistical analysis.
Note 14: The quiescent power supply current depends on the offset voltage when a practical load is connected to the amplifier.
Note 15: Output power is measured at the device terminals.
Note 16: When driving 3
or 4 loads and operating on a 5V supply, the LM4868LQ and LM4868MTE must be mounted to a circuit board that has a minimum of
2.5in
2
of exposed, uniterrupted copper area connected to the LLP or TSSOP package's exposed DAP.
Note 17: See Application Information section 'Single-Ended Output Power Performance and Measurement Considerations' for more information.
LM4868
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