April 21, 2008
LM4682
10 Watt Stereo CLASS D Audio Power Amplifier with Stereo
Headphone Amplifier and DC Volume Control
General Description
The LM4682 is a fully integrated single supply, high efficiency
audio power amplifier solution. The LM4682 utilizes a propri-
etary balanced pulse-width modulation technique that lowers
output noise and THD and improves PSRR when compared
to conventional pulse width modulators.
The LM4682 also features a stereo headphone amplifier that
delivers 60mW into a 32Ω headset with less than 0.5% THD.
The LM4682's DC volume control has a +30dB to –48dB
range when speakers are driven and a range of +13dB to –
65dB when headphones are connected. All amplifiers are
protected by thermal shutdown. Additionally, all amplifiers in-
corporate output current limiting function to protect their out-
puts from short circuit.
The LM4682 features a low-power consumption shutdown
mode. And its efficiency reaches 85% for a 10W output power
with an 8Ω load. External heatsink is not required when play-
ing music. The IC features click and pop reduction circuitry
that minimizes audible popping during device turn-on and
turn-off. The LM4682 is available in a 48-lead LLP package,
ideal for portable and desktop computer applications.
Key Specifications
■PO at THD+N = 10%, VDD = 14V 10W (typ)
■THD+N at 1kHz at 6W into 8Ω (Power Amp) 0.2% (typ)
■Efficiency at 7W into 8Ω84% (typ)
■Total quiescent power supply current 52mA (typ)
■Total shutdown power supply current 0.1mA (typ)
■THD+N 1kHz, 20mW, 32Ω (Headphone) 0.02% (typ)
■Single supply range 8.5V to 15V
Features
■Pulse-width modulator.
■DC Volume Control
■Stereo headphone amplifier.
■“Click and pop” suppression circuitry.
■Micropower shutdown mode.
■48 lead LLP package (No heatsink required).
Applications
■Flat Panel Displays
■Televisions
■Multimedia Monitors
Boomer® is a registered trademark of National Semiconductor Corporation.
© 2008 National Semiconductor Corporation 201196 www.national.com
LM4682 10 Watt Stereo CLASS D Audio Power Amplifier with Stereo Headphone Amplifier and
DC Volume Control
Block Diagram
20119622
Block Diagram for LM4682
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LM4682
Connection Diagram
LLP Package
20119618
Top View
Order Number LM4682SQ
See NS Package Number SQA48A
(LLP Package)
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LM4682
Typical Application
20119630
FIGURE 1. Typical Stereo Audio Amplifier with Headphone Selection Circuit
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LM4682
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 15.5V
Input Voltage −0.3V to VDD +0.3V
Power Dissipation (Note 3) Internally Limited
ESD Susceptibility (Note 4) 2000V
ESD Susceptibility (Note 5) 200V
Junction Temperature (Note 6) 150°C
Storage Temperature −65°C ≤ TA ≤ 150°C
Soldering Information
LLP Package
Vapor Phase (60 sec.) 215°C
Infrared (15 sec.) 220°C
See AN-450 “Surface Mounting and their Effects on Product
Reliability” for other methods of soldering surface mount
devices.
Operating Ratings (Notes 1, 2)
Temperature Range
TMIN ≤ TA ≤ TMAX −40°C ≤ TA ≤ +85°C
Supply Voltage 8.5V ≤ VDD ≤ 15V
Thermal Resistance (LLP Package)
θJA 28°C/W
θJC 20°C/W
Electrical Characteristics (Notes 1, 2, 7)
The following specifications apply for VDD = 12V, VOLVDD = 5V, RL = 8Ω, LC filter values as shown in Figure 1, unless otherwise
specified.
Limits apply for TA = 25°C.
Symbol Parameter Conditions
LM4682
Units
Typica
lMax Min
VDD Operating Supply Voltage Range 12 15 8.5 V
IS
Quiescent Power Supply Current,
Class D Mode VIN = 0VRMS, VHPSEL = 0V 52 70 mA
Quiescent Power Supply Current,
Headphone Mode VIN = 0VRMS, VHPSEL = 12V 30 40 mA
ISD
Quiescent Power Supply Current,
Shutdown Mode SDB = 0V 0.1 mA
RIN Input Resistance in Both Modes 8 kΩ
VOLVDD DC Reference Supply Voltage 5.5 3 V
VIH Minimum Logic High Input Voltage SDB, MUTEB pins 0.7xVOLVDD V
VIL Maximum Logic Low Input Voltage 0.3xVOLVDD V
VHPIH HP Sense High Input Voltage VDD-1 V
VHPIL HP Sense Low Input Voltage VDD/2 V
Power Amplifiers
POROutput Power, Per Channel THD+N ≤ 1%, fIN = 1kHz 6.0 5.5 W
PD1 Power Dissipation PO = 7W/Chan, fIN = 1kHz 2.6 W
EFF1 Efficiency PO = 7W/Chan, fIN = 1kHz 84.4 %
THD+N Harmonic Distortion + Noise PO = 6W/Chan, fIN = 1kHz 0.2 %
VNOISE
Output Noise Voltage, RMS.
A−Weighted
RSOURCE = 50Ω, CIN = 1µF,
BW = 8Hz to 22kHz
A-weighted, input referred
13
µV
PSRR Power Supply Rejection Ratio
VRIPPLE = 200mVpp, 1kHz,
VIN = 0, input referred
f = 50Hz 94
dB
f = 60Hz 94
f 100Hz 93
f = 120Hz 93
f = 1kHz 84
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LM4682
Symbol Parameter Conditions
LM4682
Units
Typica
lMax Min
Headphone Amplifiers
POPower Out Per Channel THD+N ≤ 1%, RL = 32Ω, fIN = 1kHz 80 60 mW
THD+N Distortion + Noise PO = 20mW, RL = 32Ω, fIN = 1kHz 0.02 %
VNOISE Output Noise Voltage, RMS
RIN = 50Ω, CIN = 1µF, BW = 20Hz
to 20kHz
A-weighted, input referred
9
µV
PSRR Power Supply Rejection Ratio
(Referred to Input) 200mV, 1kHz, VIN = 0, RL = 32Ω 88 dB
Electrical Characteristics for Volume Control (Notes 1, 2)
The following specifications apply for VDD = 12V. Limits apply for TA = 25°C.
Symbol Parameter Conditions
LM4682 Units
(Limits )
Typical
(Note 8)
Limit
(Note 7)
CRANGE Gain Range
VOL_CTL voltage = VOLVDD voltage,
No Load
Power Amplifier
Headphone Amplifier
30
13
29
12
dB (min)
dB (min)
VOL_CTL voltage = 0.069 x VOLVDD
No Load
Power Amplifier
Headphone Amplifier
–48
–65
–46
–63
dB (min)
dB (min)
AMMute Gain
VMUTE voltage = 0V, No Load
Power Amplifier
Headphone Amplifier
–80
–70
–60
–60
dB (max)
dB (max)
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: For operating at case temperatures above 25°C, the device must be derated based on a 150°C maximum junction temperature and a thermal resistance
of θJA = 28°C/W (junction to ambient).
Note 4: Human body model, 100pF discharged through a 1.5kΩ resistor. Device pin 16 has ESD HBM rating = 1500V.
Note 5: Machine Model 220pF−240pF discharged through all pins.
Note 6: The operating junction temperature maximum is 150°C.
Note 7: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
Note 8: Typicals are measured at 25°C and represent the parametric norm.
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LM4682
Typical Performance Characteristics (Power Amplifier)
THD+N vs Frequency
VDD = 9V, RL = 8Ω, PO = 1W
20119658
THD+N vs Frequency
VDD = 12V, RL = 8Ω, PO = 1W
20119659
THD+N vs Frequency
VDD = 15V, RL = 8Ω, PO = 1W
20119660
THD+N vs Output Power Per Channel
VDD = 9V, fIN = 1kHz, RL = 8Ω
20119661
THD+N vs Output Power Per Channel
VDD = 12V, fIN = 1kHz, RL = 8Ω
20119662
THD+N vs Output Power Per Channel
VDD = 15V, fIN = 1kHz, RL = 8Ω
20119663
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LM4682
THD+N vs Output Power Per Channel
VDD = 12V, fIN = 10kHz, RL = 8Ω
20119664
THD+N vs Output Power Per Channel
VDD = 12V, fIN = 20Hz, RL = 8Ω
20119665
Output Power vs Supply Voltage
fIN = 1kHz, RL = 8Ω
20119667
Amplifiers Gain vs Frequency
VDD = 9V, RL = 8Ω, PO = 1W
20119647
Amplifiers Gain vs Frequency
VDD = 12V, RL = 8Ω, PO = 1W
20119648
Amplifiers Gain vs Frequency
VDD = 15V, RL = 8Ω, PO = 1W
20119649
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LM4682
PSRR vs Frequency
VDD = 9V
20119644
PSRR vs Frequency
VDD = 12V
20119645
PSRR vs Frequency
VDD = 15V
20119646
Class-D Amplifier Dissipation vs Load Dissipation
Per Channel, VDD = 9V, RL = 8Ω
(both channels driven and measured)
20119638
Class-D Amplifier Dissipation vs Load Dissipation
Per Channel, VDD = 12V, RL = 8Ω
(both channels driven and measured)
20119639
Class-D Amplifier Dissipation vs Load Dissipation
Per Channel, VDD = 15V, RL = 8Ω
(both channels driven and measured)
20119640
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LM4682
Efficiency vs Output Power
VDD = 9V, RL = 8Ω
(both channels driven and measured)
20119641
Efficiency vs Output Power
VDD = 12V, RL = 8Ω
(both channels driven and measured)
20119642
Efficiency vs Output Power
VDD = 15V, RL = 8Ω
(both channels driven and measured)
20119643
Output Power vs Load Resistance
VDD = 9V, fIN = 1kHz
(both channels driven and measured)
20119655
Output Power vs Load Resistance
VDD = 12V, fIN = 1kHz
(both channels driven and measured)
20119656
Output Power vs Load Resistance
VDD = 15V, fIN = 1kHz
(both channels driven and measured)
20119657
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LM4682
Power Supply Current vs Power Supply Voltage
20119654
Class-D Amplifier Gain vs
Volume Control Voltage
VDD = 15V
20119628
Typical Performance Characteristics (Headphone Amplifier)
THD+N vs Frequency
VDD = 9V, RL = 32Ω, PO = 20mW
20119651
THD+N vs Frequency
VDD = 12V, RL = 32Ω, PO = 20mW
20119652
THD+N vs Frequency
VDD = 15V, RL = 32Ω, PO = 20mW
20119653
THD+N vs Output Power
VDD = 9V, RL = 32Ω, fIN = 1kHz
20119668
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LM4682
THD+N vs Output Power
VDD = 12V, RL = 32Ω, fIN = 1kHz
20119669
THD+N vs Output Power
VDD = 15V, RL = 32Ω, fIN = 1kHz
20119670
Output Power vs Supply Voltage Per Channel
fIN = 1kHz, RL = 32Ω
20119671
Power Supply Current vs Power Supply Voltage
20119650
Headphone Amplifier Gain vs
Volume Control Voltage
VDD = 15V
20119629
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LM4682
General Features
SYSTEM FUNCTIONAL INFORMATION
Modulation Technique
Unlike typical Class D amplifiers that use single-ended com-
parators to generate a pulse-width modulated switching
waveform and RC timing circuits to set the switching frequen-
cy, the LM4682 uses a balanced differential floating modula-
tor. Oscillation is a result of injecting complimentary currents
onto the respective plates of a floating, on-die capacitor. The
value of the floating capacitor and value of the components
in the modulator’s feedback network set the nominal switch-
ing frequency at 450kHz. Modulation results from imbalances
in the injected currents. The amount of current imbalance is
directly proportional to the applied input signal’s magnitude
and frequency.
Using a balanced, floating modulator produces a Class D am-
plifier that is immune to common mode noise sources such
as substrate noise. This noise occurs because of the high
frequency, high current switching in the amplifier’s output
stage. The LM4682 is immune to this type of noise because
the modulator, the components that set its switching frequen-
cy, and even the load all float with respect to ground.
The balanced modulator’s pulse width modulated output
drives the gates of the LM4682’s H-bridge configured output
power MOSFETs. The pulse-train present at the power MOS-
FETs’ output is applied to an LC low pass filter that removes
the 450kHz energy component. The filter’s output signal,
which is applied to the driven load, is an amplified replica of
the audio input signal.
Shutdown Function
The LM4682’s active-low shutdown function allows the user
to place the amplifier in a shutdown mode while the system
power supply remains active. Activating shutdown stops the
output switching waveform and minimizes the quiescent cur-
rent. Applying logic “0” to SDB pin enables the shutdown
function. Applying logic “1” to SDB pin disables the shutdown
function and restores full amplifier operation.
Mute Function
The LM4682’s active-low mute function allows the user to
place the amplifier outputs in muted mode while the
amplifier’s analog input signals remain active. Activating mute
internally removes the analog input signal from the Class D
and headphone amplifier inputs. While muted the amplifier
inputs and outputs retain in their VDD/2 operational bias. Ap-
plying logic “0” to MUTEB pin activates mute. Applying logic
“1” to MUTEB pin deactivates mute. The MUTEB pin is pull-
down internally to put both Class D and headphone amplifier
outputs mute.
Stereo Headphone Amplifier
The LM4682’s stereo headphone amplifier operates continu-
ously, even while the Class D amplifiers are active. When
using headphones to listen to program material, it is usually
desirable to stop driving external speakers. This is easily
achieved by using the active high HPSEL input. As shown in
typical application schematic in Figure 1, with no headphones
connected to the headphone jack, the input voltage applied
to the HPSEL pin is a logic low. In this state, the Class D am-
plifiers are active and able to drive external speakers. When
headphones are plugged into the headphone jack, the switch
inside the jack is opened. This changes the voltage applied
to the HPSEL pin to a logic high, shutting off the LM4682’s
Class D amplifiers. The headphone control of the output con-
figuration is shown in Table 1.
TABLE 1. Headphone Controls
HP Sense Pin, HPSEL Output Stage Configuration
0 Class D Amps Active
1 Class D Amps Inactive
Under Voltage Protection
The under voltage protection disables the output driver sec-
tion of the LM4682 while the supply voltage is below 8V. This
condition may occur as power is first applied or during low line
conditions, changes in load resistance, or when power supply
sag occurs. The under voltage protection ensures that all of
the LM4682’s power MOSFETs are off. This action eliminates
shoot-through current and minimizes output transients during
turn-on and turn-off. The under voltage protection gives the
digital logic time to stabilize into known states, further mini-
mizing turn on output transients.
Power Supply Sequencing
In order to stabilize LM4682 before any operation, a power-
up sequence for the power supplies is recommended. The
Power VDD should be applied first. Without deactivating the
mute and shutdown function of the amplifiers, the VOLVDD is
then applied. Prior to removing the two supply voltages, acti-
vate shutdown and mute.
Turn-On Time
The LM4682 has an internal timer that determines the
amplifier’s turn-on time. After power is first applied or the part
returns from shutdown, the nominal turn-on time is 600ms.
This delay allows all externally applied capacitors to charge
to a final value of VDD/2. Further, during turn-on, the outputs
are muted. This minimizes output transients that may occur
while the part settles into its quiescent operating mode.
Output Stage Current Limit and Fault Detection
Protection
The output stage MOSFETs are protected against output
conditions that could otherwise compromise their operational
status. The first stage of protection is output current limiting.
When conditions that require high currents to drive a load, the
LM4682’s current limit circuitry clamps the output current at a
nominal value of 2.5A. The output waveform is present, but
may be clipped or its amplitude reduced. The same 2.5A
nominal current limit also occurs if the amplifier outputs are
shorted together or either output is shorted to VDD or GND.
The second stage of protection is an onboard fault detection
circuit that continuously monitors the signal on each output
MOSFET’s gate and compares it against the respective drain
voltage. When a condition is detected that violates a
MOSFET’s Safe Operating Area (SOA) and the drive signal
is disconnected from the output MOSFETs’ gates. The fault
detect circuit maintains this protective condition for approxi-
mately 600ms, at which time the drive signal is reconnected.
If the fault condition is no longer present, normal operation
resumes. If the fault condition remains, however, the drive
signal is again disconnected.
Thermal Protection
The LM4682 has thermal shutdown circuitry that monitors the
die temperature. Once the LM4682 die temperature reaches
170°C, the LM4682 disables the output switching waveform
and remains disabled until the die temperature falls below
140°C (typ).
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LM4682
Over-Modulation Protection
The LM4682’s over-modulation protection is a result of the
preamplifier’s inability to produce signal magnitudes that
equal the power supply voltages. Since the preamplifier’s out-
put magnitude will always be less than the supply voltage, the
duty cycle of the amplifier’s switching output will never reach
zero. Peak modulation is limited to a nominal 95%.
DC Volume Control
The LM4682 has an internal stereo volume control whose
setting is a function of the DC voltage applied to the volume
control pin VOLCTL.
The LM4682 volume control consists of 31 steps, which are
individually selected by a variable DC voltage level on the
VOLCTL pin. A linear type 100kΩ potentiometer is used to
adjust the VOLCTL voltage in the LM4682 demonstration
board as shown in application circuit (see Figure 1). The re-
sistance value of potentiometer fall in the range from 10kΩ to
100kΩ is recommended to be used with only small amount of
current dissipation and large enough for the VOLCTL pin to
function properly. The Volume Control Characteristics of
LM4682 can be found in the Typical Performance Character-
istics section. The gain range of Class D amplifiers are from
–48dB to 30dB. The gain range of headphone amplifiers are
from –65dB to 13dB. Each gain step corresponds to specific
input voltage of both Class D amplifiers and headphone am-
plifiers are shown in Table 2.
To minimize the effect of noise on the volume control VOLCTL
pin, which can affect the selected gain level, hysteresis has
been implemented. The amount of hysteresis corresponds to
half of the step width. For highest accuracy, the voltage shown
in the “recommended voltage” column of the table is used to
select a desired gain. The recommended voltage is exactly
halfway between the two closest transitions to the next high-
est or next lowest gain levels.
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LM4682
TABLE 2. Volume Control Table
Voltage Range (% of VOLVDD) Voltage Range (V), VOLVDD = 5V Gain (dB)
Step Low High Recommended Low High Recommended Class D
Amplifier
Headphone
Amplifier
1 77.50% 100.00% 100.000% 3.875 5.000 5.000 29.97 13.06
2 75.00% 78.50% 76.875% 3.750 3.925 3.844 28.97 12.07
3 72.50% 76.25% 74.375% 3.625 3.813 3.719 27.97 11.07
4 70.00% 73.75% 71.875% 3.500 3.688 3.594 26.96 10.06
5 67.50% 71.25% 69.375% 3.375 3.563 3.469 25.98 9.07
6 65.00% 68.75% 66.875% 3.250 3.438 3.344 24.97 8.07
7 62.50% 66.25% 64.375% 3.125 3.313 3.219 23.95 7.05
8 60.00% 63.75% 61.875% 3.000 3.188 3.094 21.98 5.08
9 57.50% 61.25% 59.375% 2.875 3.063 2.969 19.95 3.05
10 55.00% 58.75% 56.785% 2.750 2.983 2.844 17.96 1.06
11 52.50% 56.25% 54.375% 2.625 2.813 2.719 15.97 –0.93
12 50.00% 53.75% 51.875% 2.500 2.688 2.594 13.99 –2.91
13 47.50% 51.25% 49.375% 2.375 2.563 2.469 11.99 –4.91
14 45.00% 48.75% 46.875% 2.250 2.438 2.344 9.95 –6.96
15 42.50% 46.25% 44.375% 2.125 2.313 2.219 7.96 –8.94
16 40.00% 43.75% 41.875% 2.000 2.188 2.094 5.96 –10.95
17 37.50% 41.25% 39.375% 1.875 2.063 1.969 3.99 –12.91
18 35.00% 38.75% 36.875% 1.750 1.938 1.844 2.03 –14.87
19 32.50% 36.25% 34.375% 1.625 1.813 1.719 –0.02 –16.92
20 30.00% 33.75% 31.875% 1.500 1.688 1.594 –2.11 –19.02
21 27.50% 31.25% 29.375% 1.375 1.563 1.469 –4.16 –21.06
22 25.00% 28.75% 26.875% 1.250 1.438 1.344 –5.97 –22.87
23 22.50% 26.25% 24.375% 1.125 1.313 1.219 –8.77 –25.68
24 20.00% 23.75% 21.875% 1.000 1.188 1.094 –12.06 –28.96
25 17.50% 21.25% 19.375% 0.875 1.063 0.969 –14.84 –31.75
26 15.00% 18.75% 16.875% 0.750 0.938 0.844 –17.36 –34.26
27 12.50% 16.25% 14.375% 0.625 0.813 0.719 –20.89 –37.79
28 10.00% 13.75% 11.875% 0.500 0.688 0.594 –26.92 –43.83
29 7.50% 11.25% 9.375% 0.375 0.563 0.469 –32.95 –49.85
30 5.00% 8.75% 6.875% 0.250 0.438 0.344 –38.97 –55.88
31 0.00% 6.25% 0.000% 0.000 0.313 0.000 –48.03 –64.94
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LM4682
Application Hints
SUPPLY BYPASSING
The major source of noises to be taken care and applying
bypassing technique in using LM4682 are those transients
response coming from its output stage. During the switching
operations of the output stage of LM4682, the switching fre-
quencies vary when the internal modulator react to the input
signals. This creates a band of switching transients giving
back to the power supply terminals of LM4682. A single ca-
pacitor may not bypass those transients well. Two capacitors
which values are closed to each other are used to bypass this
range of frequencies to the ground. 10μF tantalum capacitors
and 4.7μF ceramic capacitors are needed for this kind of de-
coupling of LM4682 switching operation. This results an im-
provement in terms of both stability and audio performance of
LM4682. In addition, these capacitors should be placed as
close as possible to each IC’s supply pin(s) using leads as
short as possible. Apart from the power supply de-coupling
capacitors, the four bootstrapping capacitors (at pins
BST1_A, BST2_A, BST1_B and BST2_B) should also be
placed close to their corresponding pins. This could minimize
the undesirable switching noise coupled to the supply rail.
The LM4682 has two different sets of VDD pins: a set for power
VDD (PVDD_A and P VDD _B) and a set for signal VDD _A and
HP_ VDD. The parallel combination of the low value ceramic
(4.7μF) and high value tantalum (10μF) should be used to
bypass the power VDD pins. A small value (1μF) ceramic or
tantalum can be used to bypass the signal VDD _A and HP_
VDD pin.
OUTPUT STAGE FILTERING
The LM4682 requires a low pass filter connected between the
amplifier’s bridge output and the load. Figure 1 shows the
recommended LC filter. A minimum value of 22µH is recom-
mended. As shown in Figure 1, using the values of the com-
ponents connected between the amplifier BTL outputs and
the load achieves a 2nd-order lowpass filter response which
optimizes the amplifier's performance within the audio band.
THD+N MEASUREMENTS AND OUT OF AUDIO BAND
NOISE
THD+N (Total Harmonic Distortion plus Noise) is a very im-
portant parameter by which all audio amplifiers are measured.
Often it is shown as a graph where either the output power or
frequency is changed over the operating range. A very im-
portant variable in the measurement of THD+N is the band-
width-limiting filter at the input of the test equipment. Class D
amplifiers, by design, switch their output power devices at a
much higher frequency than the accepted audio range (20Hz
- 20kHz). Alternately switching the output voltage between
VDD and GND allows the LM4682 to operate at much higher
efficiency than that achieved by traditional Class AB ampli-
fiers. Switching the outputs at high frequency also increases
the out-of-band noise. Under normal circumstances the out-
put lowpass filter significantly reduces this out-of-band noise.
If the low pass filter is not optimized for a given switching fre-
quency, there can be significant increase in out-of-band
noise. THD+N measurements can be significantly affected by
out-of-band noise, resulting in a higher than expected THD+N
measurement. To achieve a more accurate measurement of
THD, the test equipment’s input bandwidth of the must be
limited. Some common upper filter points are 22kHz, 30kHz,
and 80kHz. The input filter limits the noise component of the
THD+N measurement to a smaller bandwidth resulting in a
more real-world THD+N value.
RECOMMENDED PRINTED CIRCUIT BOARD LAYOUT
Figures 2 through 6 show the recommended four-layer PCB
board layout that is optimized for the 48-pin LLP packaged
LM4682 and associated external components. This circuit is
designed for use with an external 12V supply and 8Ω speak-
ers (or load resistors). Apply 12V and ground to board’s VDD
and GND terminals respectively. And apply 5V to the
VOLVDD (refer to power supply sequencing for details). Con-
nect speakers (or load resistors) between the board’s OUTA
+ and OUTA-, and between the board’s OUTB+ and OUTB-.
Apply the stereo input signals to IN_A and IN_B. When de-
signing the layout of the PCB layout, please pay attention to
the output terminals of LM4682.
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LM4682
20119626
FIGURE 2. Top Layer
20119627
FIGURE 3. Top Silkscreen Layer
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LM4682
20119623
FIGURE 4. Upper Middle Layer
20119624
FIGURE 5. Lower Middle Layer
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LM4682
20119625
FIGURE 6. Bottom Layer
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LM4682
Revision History
Rev Date Description
1.0 02/22/06 Initial WEB release of the document.
1.1 02/24/06 Edited art 201196 71 (changed the y-axis unit from mA to mW.
1.2 03/08/06 Did few texts clean-up and re-released D/S to the WEB (per Kevin H.).
1.3 06/29/06 Added 2 columns on ( Gain dB) Table 2 and re-released the D/S to the
WEB (per Alex CK Wong).
1.4 04/09/08 Added volume control curves and input some text edits.
1.5 04/15/08 Changed the titles on curves 20119628 and 29.
1.6 04/21/08 Text edits.
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LM4682
Physical Dimensions inches (millimeters) unless otherwise noted
Order Number LM4682SQ
NS Package Number SQA48A
21 www.national.com
LM4682
Notes
LM4682 10 Watt Stereo CLASS D Audio Power Amplifier with Stereo Headphone Amplifier and
DC Volume Control
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