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LM4680
10W High-Efficiency Mono BTL Audio Power Amplifier
General Description
The LM4680 is a high efficiency switching audio power
amplifier primarily designed for demanding applications in
flat panel monitors and TV's. It is capable of delivering 10W
to an 8
mono BTL load with less than 10% distortion
(THD+N) when powered from a 14V
DC
power supply.
Boomer audio power amplifiers were designed specifically to
provide high quality output power with a minimal amount of
external components. The LM4680 features a micro-power,
active-low shutdown mode, an internal thermal shutdown
protection mechanism, output fault detect, and short circuit
protection.
The LM4680 contains advanced transient ("pop and click")
suppression circuitry that eliminates noises that would oth-
erwise occur during turn-on and turn-off transitions.
Key Specifications
j
Power Output BTL (V
DD
= 14V,
f
IN
= 1kHz, THD+N = 10%,
R
L
= 8
)
10W (typ)
j
Quiescent Power Supply Current
25mA (typ)
j
Efficiency (V
DD
= 12V, f
IN
= 1kHz,
R
L
= 8
, P
OUT
= 6W)
81% (typ)
j
Shutdown Current
0.1mA (typ)
j
Fixed Gain
30dB (typ)
Features
n
Soft-start circuitry eliminates noise during turn-on
transition
n
Low current shutdown mode
n
Low quiescent current
n
6W BTL output, R
L
= 8
, THD+N = 1%
n
Short circuit protection
n
Fixed, internally set gain of 30dB
n
Internal clamp diodes protect amplifier outputs
Applications
n
Flat Panel Monitors
n
Flat Panel TVs
n
Computer Sound Cards
Connection Diagram
Plastic Package
20095802
Top View
Order Number LM4680SD
See NS Package Number SRC14A
Boomer
is a registered trademark of National Semiconductor Corporation.
January 2005
LM4680
10W
High-Efficiency
Mono
BTL
Audio
Power
Amplifier
2005 National Semiconductor Corporation
DS200958
www.national.com
Typical Application
LM4680SD Demo Board Bill of Material
Item
Part Description
Package Size
Qty
Ref Designator
Remark
Supplier
1
LM4680SD Audio Amplifier
LLP14
1
U1
2
Cer Cap 0.1F 16V 10%
0805
1
C4
PCC1812CT-ND
Digi - Key
3
Cer Cap 0.27F 16V 10%
0805
3
C5, C7, C8
PCC1916CT-ND
Digi - Key
4
Cer Cap 1.0F 25V 10%
0805
2
C1 - C2
PCC2319CT-ND
Digi - Key
5
Tant Cap 1.0F 16V 10%
Size = A (3216)
2
C9
399-1583-2-ND
Digi - Key
6
Tant Cap 10.0F 16V 10%
Size = A (3216)
2
C10
478-1655-2-ND
Digi - Key
7
Tant Cap 10.0F 16V 10%
Size = A (3216)
1
C3
478-1655-2-ND
Digi - Key
8
Inductor 4922 Series 27H
SMT
2
L1, L2
DN2218CT-ND
Digi - Key
20095801
FIGURE 1. Typical Audio Amplifier Application Circuit
LM4680
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2
Absolute Maximum Ratings
(Notes 1, 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage
16V
Storage Temperature
-65C to +150C
Input Voltage
-0.3V to V
DD
+0.3V
Power Dissipation (Note 3)
Internally limited
ESD Susceptibility(Note 4)
2000V
ESD Susceptibility (Note 5)
200V
Junction Temperature
150C
Thermal Resistance
JC
(LD)
2C/W
JA
(LD)
40C/W
Operating Ratings
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
85C
Supply Voltage (Note 10)
9.0V
V
DD
14V
Electrical Characteristics for the LM4680
(Note 1)
The following specifications apply for the circuit shown in Figure 1 operating with V
DD
= 12V, R
L
= 8
, and f
IN
= 1kHz,
unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4680
Units
(Limits)
Typical
Limit
(Note 6)
(Notes 7,
8)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, I
O
= 0A, R
L
= 8
28
52
mA
I
SD
Shutdown Current
V
SHUTDOWN
= GND (Note 9)
0.1
mA
A
V
Amplifier Gain
BTL output voltage with respect to input
voltage
30
dB
P
O
Output Power
THD+N = 1% (max)
THD+N = 10%, V
DD
= 14V
6
10
5
W
THD+N
Total Harmonic Distortion + Noise
P
OUT
= 1W
RMS
0.2
%
f
BW
Frequency Response Bandwidth
P
OUT
= 6W, post filter,
-3dB relative to 1kHz
20
20000
Hz
Hz
Efficiency
P
OUT
= 6W
81
%
N
Output Noise
A-Weighted Filter, V
IN
= 0V,
Input Referred
10
V
SNR
Signal-to-Noise Ratio
A-Weighted Filter, P
OUT
= 6W
Input Referred
116
dB
PSRR
Power Supply Rejection Ratio
V
RIPPLE
= 200mV
p-p
, C
BYPASS_1
= 10F,
Input Referred
f = 50Hz
f = 60Hz
f = 100Hz
f = 120Hz
f = 1kHz
99
101
102
102
104
dB
t
WU
Wake-Up time
C
BYPASS
= 10F
600
ms
T
SD
Thermal Shutdown Temperature
170
C
C
V
SDIH
Shutdown Voltage Input High
4
V (min)
V
SDIL
Shutdown Voltage Input Low
1.5
V (max)
LM4680
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3
Note 1: All voltages are measured with respect to the GND 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 Absolute Maximum Ratings, whichever is lower. For the LM4680 typical application
(shown in Figure 1) with V
DD
= 12V, R
L
= 8
stereo operation, the total power dissipation is 900mW.
JA
= 40C/W
Note 4: Human body model, 100pF discharged through a 1.5k
resistor.
Note 5: Machine model, 220pF 240pF discharged through all pins.
Note 6: Typicals are measured at 25C and represent the parametric norm.
Note 7: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
Note 8: Datasheets min/max specification limits are guaranteed by design, test, or statistical analysis.
Note 9: Shutdown current is measured in a normal room environment. The SHUTDOWN pin should be driven as close as possible to GND for minimum shutdown
current.
Note 10: Please refer to "Under Voltage Protection" on page 8 under "General Features."
Typical Performance Characteristics
THD+N vs Frequency
V
DD
= 9V, R
L
= 8
, P
O
= 1W
THD+N vs Frequency
V
DD
= 12V, R
L
= 8
, P
O
= 1W
20095806
20095807
THD+N vs Frequency
V
DD
= 14V, R
L
= 8
, P
O
= 1W
THD+N vs Output Power
R
L
= 8
, V
DD
= 9V, f = 1kHz
20095808
20095809
LM4680
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4
Typical Performance Characteristics
(Continued)
THD+N vs Output Power
R
L
= 8
, V
DD
= 12V, f = 1kHz
THD+N vs Output Power
R
L
= 8
, V
DD
= 14V, f = 1kHz
20095810
20095811
Amplifier Output Power
vs Power Supply Voltage
R
L
= 8
, f = 1kHz
Amplifier Output Magnitude
vs Frequency
R
L
= 8
, V
DD
= 12V
20095812
20095813
Power Rejection Ratio vs Frequency
V
DD
= 9V, R
L
= 8
, Input Referred
Power Rejection Ratio vs Frequency
V
DD
= 12V, R
L
= 8
, Input Referred
20095825
20095826
LM4680
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