LM4882MM/NOPB [ROCHESTER]
0.48W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO8, MSOP-8;
| 型号： | LM4882MM/NOPB |
| 厂家： | 
Rochester Electronics |
| 描述： | 0.48W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO8, MSOP-8 放大器 光电二极管 商用集成电路 |
| 文件： | 总16页 (文件大小：1197K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
January 2003
LM4882
250mW Audio Power Amplifier with Shutdown Mode
j
General Description
The LM4882 is a single-ended audio power amplifier ca-
pable of delivering 250mW of continuous average power into
an 8Ω load with 1% THD+N from a 5V power supply.
THD+N at 1kHz at 85mW
continuous average output
power into 32Ω
0.1% (typ)
0.7µA (typ)
j
Shutdown Current
Boomer® audio power amplifiers were designed specifically
to provide high quality output power with a minimal amount
of external components using surface mount packaging.
Since the LM4882 does not require bootstrap capacitors or
snubber networks, it is optimally suited for low-power por-
table systems.
Features
n MSOP surface mount packaging
n “Click and Pop” Suppression Circuitry
n Supply voltages from 2.4V–5.5V
n Operating Temperature −40˚C to 85˚C
n Unity-gain stable
The LM4882 features an externally controlled, low power
consumption shutdown mode which is virtually clickless and
popless, as well as an internal thermal shutdown protection
mechanism.
n External gain configuration capability
n No bootstrap capacitors, or snubber circuits are
The unity-gain stable LM4882 can be configured by external
gain-setting resistors.
necessary
Applications
n Personal Computers
n Cellular Phones
Key Specifications
j
j
THD+N at 1kHz at 250mW
continuous average output
power into 8Ω
n General Purpose Audio
1.0% (max)
Output Power at 1% THD+N
at 1kHz into 4Ω
380mW (typ)
Typical Application
10003001
*Refer to the Application Information Section for information concerning proper selection of the input and output coupling capacitors.
FIGURE 1. Typical Audio Amplifier Application Circuit
Boomer® is a registered trademark of National Semiconductor Corporation.
© 2003 National Semiconductor Corporation
DS100030
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Connection Diagrams
MSOP and SOIC Package
Die Layout (A Step)
10003042
10003002
Order Number LM4882 MDA
See NS Package Number MDA
Top View
Order Number LM4882MM or LM4882M
See NS Package Number MUA08A or M08A
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2
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
See AN-450 "Surface Mounting and their Effects on
Product Reliability" for other methods of soldering surface
mount devices.
Thermal Resistance
Supply Voltage
6.0 V
−65˚C to +150˚C
−0.3V to VDD + 0.3V
Internally limited
2000V
θJC (MSOP)
θJA (MSOP)
θJC (SOP)
θJA (SOP)
56˚C/W
210˚C/W
35˚C/W
Storage Temperature
Input Voltage
Power Dissipation (Note 3)
ESD Susceptibility (Note 4)
PIn 5
170˚C/W
1500V
Operating Ratings
Temperature Range
TMIN ≤ TA ≤ TMAX
Supply Voltage
Junction Temperature
Soldering Information
Small Outline Package
Vapor Phase (60 seconds)
Infrared (15 seconds)
150˚C
−40˚C ≤ TA ≤ 85˚C
2.4V ≤ VDD ≤ 5.5V
215˚C
220˚C
Electrical Characteristics (Notes 1, 2)
The following specifications apply for VDD = 5V unless otherwise specified. Limits apply for TA = 25˚C.
LM4882
Typical Limit
Units
(Limits)
Symbol
Parameter
Conditions
(Note 5)
(Note 6)
IDD
ISD
Quiescent Current
VIN = 0V, IO = 0A
2
0.5
5
4.0
5
mA (max)
µA (max)
mV (max)
Shutdown Current
Offset Voltage
Output Power
Vpin1 = VDD
VOS
P O
VIN = 0V
50
THD + N = 1% (max); f = 1 kHz;
RL = 4Ω
380
270
95
mW
mW (min)
mW
RL = 8Ω
250
RL = 32Ω
THD + N = 10%; f = 1 kHz
RL = 4Ω
480
325
125
0.5
mW
mW
mW
%
RL = 8Ω
RL = 32Ω
THD + N
PSRR
Total Harmonic Distortion + Noise
Power Supply Rejection Ratio
RL = 8Ω, P = 250 mWrms;
O
RL = 32Ω, PO = 85 mWrms;
0.1
%
f = 1 kHz
Vpin3 = 2.5V, V
f = 120 Hz
= 200 mVrms,
ripple
50
dB
Electrical Characteristics (Notes 1, 2)
The following specifications apply for VDD = 3V unless otherwise specified. Limits apply for TA = 25˚C.
LM4882
Units
(Limits)
Symbol
Parameter
Conditions
Typical
(Note 5)
1.2
Limit
(Note 6)
IDD
ISD
Quiescent Current
VIN = 0V, IO = 0A
mA
µA
Shutdown Current
Offset Voltage
Output Power
Vpin1 = VDD
0.3
VOS
P O
VIN = 0V
5
mV
THD + N = 1% (max); f = 1 kHz
RL = 8Ω
80
30
mW
mW
RL = 32Ω
THD + N = 10%; f = 1 kHz
RL = 8Ω
105
40
mW
mW
RL = 32Ω
3
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Electrical Characteristics (Notes 1, 2) (Continued)
The following specifications apply for VDD = 3V unless otherwise specified. Limits apply for TA = 25˚C.
LM4882
Units
(Limits)
Symbol
THD + N
Parameter
Conditions
Typical
Limit
(Note 5)
0.25
(Note 6)
Total Harmonic Distortion + Noise
RL = 8Ω, P = 70 mWrms;
%
%
O
RL = 32Ω, PO = 30 mWrms;
0.3
f = 1 kHz
PSRR
Power Supply Rejection Ratio
Vpin3 = 2.5V, V
f = 120 Hz
= 200 mVrms,
ripple
50
dB
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 Characteristicsstate 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
, θ , and the ambient temperature T . The maximum
A
JMAX JA
allowable power dissipation is P
= (T
− T )/θ . For the LM4882, T
= 150˚C, and the typical junction-to-ambient thermal resistance, when board
DMAX
JMAX
A
JA
JMAX
mounted, is 210˚C/W for the MUA08A Package and 170˚C/W for the M08A Package.
Note 4: Human body model, 100 pF discharged through a 1.5 kΩ resistor.
Note 5: Typicals are measured at 25˚C and represent the parametric norm.
Note 6: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).
External Components Description
(Refer to Figure 1)
Components
Functional Description
1. Ri
Inverting input resistance which sets the closed-loop gain in conjunction with Rf. This resistor also forms a high
pass filter with Ci at fc = 1 / (2πRiCi).
2. Ci
Input coupling capacitor which blocks the DC voltage at the amplifier’s input terminals. Also creates a highpass
filter with Ri at fc = 1 / (2πRiC ). Refer to the section, Proper Selection of External Components, for an
i
explanation of how to determine the values of Ci.
3. Rf
Feedback resistance which sets closed-loop gain in conjunction with Ri.
Supply bypass capacitor which provides power supply filtering. Refer to the Application Information section
for proper placement and selection of the supply bypass capacitor.
4. CS
5. CB
6. CO
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 CB.
Output coupling capacitor which blocks the DC voltage at the amplifier’s output. Forms a high pass filter wth RL
at fO = 1 / (2πRLC O).
Typical Performance Characteristics
THD+N vs Frequency
THD+N vs Frequency
10003026
10003009
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Typical Performance Characteristics (Continued)
THD+N vs Frequency
THD+N vs Frequency
10003011
10003010
THD+N vs Frequency
THD+N vs Frequency
10003023
10003022
THD+N vs Frequency
THD+N vs Frequency
10003024
10003025
5
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Typical Performance Characteristics (Continued)
THD+N vs
THD+N vs
Output Power
Output Power
10003029
10003004
THD+N vs
THD+N vs
Output Power
Output Power
10003030
10003008
THD+N vs
THD+N vs
Output Power
Output Power
10003018
10003019
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Typical Performance Characteristics (Continued)
THD+N vs
THD+N vs
Output Power
Output Power
10003020
10003021
10003013
10003028
Output Power vs
Supply Voltage
Output Power vs
Supply Voltage
10003012
Output Power vs
Supply Voltage
Dropout Voltage vs
Supply Voltage
10003014
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Typical Performance Characteristics (Continued)
Dropout Voltage vs
Supply Voltage
Power Supply
Rejection Ratio
10003037
10003038
Output Power vs
Load Resistance
Power Dissipation vs
Output Power
10003015
10003027
Supply Current vs
Supply Voltage
Open Loop
Frequency Response
10003016
10003036
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Typical Performance Characteristics (Continued)
Output Attenuation in
Shutdown Mode
Noise Floor
10003006
10003007
Frequency Response
Frequency Response
vs Output Capacitor Size
vs Output Capacitor Size
10003031
10003032
Frequency Response
vs Input Capacitor Size
Typical Application
Frequency Response
10003033
10003034
9
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Typical Performance Characteristics (Continued)
Typical Application
Frequency Response
Power Derating Curve
10003039
10003035
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possible. As displayed in the Typical Performance Charac-
teristics section, the effect of a larger half supply bypass
capacitor is improved low frequency PSRR due to increased
half-supply stability. Typical applications employ a 5V regu-
lator with 10 µF and a 0.1 µF bypass capacitors which aid in
supply stability, but do not eliminate the need for bypassing
the supply nodes of the LM4882. The selection of bypass
capacitors, especially CB, is thus dependent upon desired
low frequency PSRR, click and pop performance as ex-
plained in the section, Proper Selection of External Com-
ponents section, system cost, and size constraints.
Application Information
SHUTDOWN FUNCTION
In order to reduce power consumption while not in use, the
LM4882 contains a shutdown pin to externally turn off the
amplifier’s bias circuitry. This shutdown features turns the
amplifier off when a logic high is placed on the shutdown pin.
The trigger point between a logic low and logic high level is
typically half supply. It is best to switch between ground and
supply to provide maximum device performance. By switch-
ing the shutdown pin to the VDD, the LM4882 supply current
draw will be minimized in idle mode. While the device will be
disabled with shutdown pin voltages less than V DD, the idle
current may be greater than the typical value of 0.5 µA. In
either case, the shutdown pin should be tied to a definite
voltage because leaving the pin floating may result in an
unwanted shutdown condition. In many applications, a mi-
crocontroller or microprocessor output is used to control the
shutdown circuitry which provides a quick smooth transition
into shutdown. Another solution is to use a single-pole,
single-throw switch in conjunction with an external pull-up
resistor. When the switch is closed, the shutdown pin is
connected to ground and enables the amplifier. If the switch
is open, then the external pull-up resistor will disable the
LM4882. This scheme guarantees that the shutdown pin will
not float which will prevent unwanted state changes.
PROPER SELECTION OF EXTERNAL COMPONENTS
Selection of external components when using integrated
power amplifiers is critical to optimize device and system
performance. While the LM4882 is tolerant of external com-
ponent combinations, consideration to component values
must be used to maximize overall system quality.
The LM4882 is unity gain stable and this gives a designer
maximum system flexibility. The LM4882 should be used in
low gain configurations to minimize THD+N values, and
maximize the signal to noise ratio. Low gain configuartions
require large input signals to obtain a given output power.
Input signals equal to or greater than 1 Vrms are available
from sources such as audio codecs. Please refer to the
section, Audio Power Amplifier Design, for a more com-
plete explanation of proper gain selection.
POWER DISSIPATION
Besides gain, one of the major considerations is the closed
loop bandwidth of the amplifier. To a large extent, the band-
width is dictated by the choice of external components
shown in Figure 1. Both the input coupling capacitor, Ci, and
the output coupling capacitor, Co, form first order high pass
filters which limit low frequency response. These values
should be chosen based on needed frequency response for
a few distinct reasons.
Power dissipation is a major concern when using any power
amplifier and must be thoroughly understood to ensure a
successful design. Equation 1 states the maximum power
dissipation point for a single-ended amplifier operating at a
given supply voltage and driving a specified output load.
PDMAX = (VDD
)
2/(2π2RL)
(1)
Even with this internal power dissipation, the LM4882 does
not require heat sinking over a large range of ambient tem-
perature. From Equation 1, assuming a 5V power supply and
an 4Ω load, the maximum power dissipation point is
316 mW. The maximum power dissipation point obtained
must not be greater than the power dissipation that results
from Equation 2:
CLICK AND POP CIRCUITRY
The LM4882 contains circuitry to minimize turn-on and turn-
off transients or “clicks and pops.” In this case, turn-on refers
to either power supply turn-on or the device coming out of
shutdown mode. When the device is turning on, the amplifi-
ers are internally muted. An internal current source ramps up
the voltage of the bypass pin. Both the inputs and outputs
track the voltage at the bypass pin. The device will remain
muted until the bypass pin has reached its half supply volt-
age, 1/2 VDD. As soon as the bypass node is stable, the
device will become fully operational, where the gain is set by
the external resistors.
PDMAX = (TJMAX−T A)/θJA
(2)
For the LM4882 surface mount package, θJA = 210˚C/W and
TJMAX = 150˚C. Depending on the ambient temperature, TA,
of the system surroundings, Equation 2 can be used to find
the maximum internal power dissipation supported by the IC
packaging. If the result of Equation 1 is greater than that of
Equation 2, then either the supply voltage must be de-
creased, the load impedance increased or T A reduced. For
the typical application of a 5V power supply, with an 4Ω load,
the maximum ambient temperature possible without violating
the maximum junction temperature is approximately 83˚C
provided that device operation is around the maximum
power dissipation point. Power dissipation is a function of
output power and thus, if typical operation is not around the
maximum power dissipation point, the ambient temperature
may be increased accordingly. Refer to the Typical Perfor-
mance Characteristics curves for power dissipation infor-
mation for lower output powers.
Although the bypass pin current source cannot be modified,
the size of CB can be changed to alter the device turn-on
time and the level of “clicks and pops.” By increasing the
value of C B, the level of turn-on pop can be reduced.
However, the tradeoff for using a larger bypass capacitor is
an increase in turn-on time for the device. There is a linear
relationship between the size of CB and the turn-on time.
Here are some typical turn-on times for a given CB:
CB
TON
0.01 µF
0.1 µF
0.22 µF
0.47 µF
20 ms
200 ms
420 ms
900 ms
POWER SUPPLY BYPASSING
As with any power amplifier, proper supply bypassing is
critical for low noise performance and high power supply
rejection. The capacitor location on both the bypass and
power supply pins should be as close to the device as
In order to eliminate “clicks and pops,” all capacitors must be
discharged before turn-on. Rapid on/off switching of the
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from adding VOPEAK and VOD. Since 5V is a standard supply
voltage in most applications, it is chosen for the supply rail.
Extra supply voltage creates headroom that allows the
LM4882 to reproduce peaks in excess of 300 mW without
clipping the signal. At this time, the designer must make sure
that the power supply choice along with the output imped-
ance does not violate the conditions explained in the Power
Dissipation section.
Application Information (Continued)
device or the shutdown function may cause the “click and
pop” circuitry to not operate fully, resulting in increased “click
and pop” noise.
The value of Ci will also reflect turn-on pops. Clearly, a
certain size for Ci is needed to couple in low frequencies
without excessive attenuation. But in many cases, the
speakers used in portable systems have little ability to repro-
duce signals below 100 Hz to 150 Hz. In this case, using a
large input and output coupling capacitor may not increase
system performance. In most cases, choosing a small value
of Ci in the range of 0.1 µF to 0.33 µF, along with CB equal to
1.0 µF should produce a virtually clickless and popless turn-
Once the power dissipation equations have been addressed,
the required gain can be determined from Equation 4.
(4)
AV = Rf / Ri
(5)
on. In cases where C is larger than 0.33 µF, it may be
i
From Equation 4, the minimum gain is:
AV = 1.4
advantageous to increase the value of CB. Again, it should
be understood that increasing the value of CB will reduce the
“clicks and pops” at the expense of a longer device turn-on
time.
Since the desired input impedance was 20 kΩ, and with a
gain of 1.4, a value of 28 kΩ is designated for Rf, assuming
5% tolerance resistors. This combination results in a nominal
gain of 1.4. The final design step is to address the bandwidth
requirements which must be stated as a pair of −3 dB
frequency points. Five times away from a −3 dB point is
0.17 dB down from passband response assuming a single
pole roll-off. As stated in the External Components section,
AUDIO POWER AMPLIFIER DESIGN
Design a 250 mW/8Ω Audio Amplifier
Given:
Power Output
Load Impedance
Input Level
250 mWrms
both Ri in conjunction with C , and Co with RL, create first
8Ω
1 Vrms (max)
i
order highpass filters. Thus to obtain the desired frequency
low response of 100 Hz within 0.5 dB, both poles must be
taken into consideration. The combination of two single order
filters at the same frequency forms a second order response.
This results in a signal which is down 0.34 dB at five times
away from the single order filter −3 dB point. Thus, a fre-
quency of 20 Hz is used in the following equations to ensure
that the response is better than 0.5 dB down at 100 Hz.
Input Impedance
Bandwidth
20 kΩ
100 Hz–20 kHz 0.50 dB
A designer must first determine the needed supply rail to
obtain the specified output power. Calculating the required
supply rail involves knowing two parameters, VOPEAK and
also the dropout voltage. The latter is typically 530mV and
can be found from the graphs in the Typical Performance
Characteristics. VOPEAK can be determined from Equation
3.
Ci ≥ 1 / (2π * 20 kΩ * 20 Hz) = 0.397 µF; use 0.39 µF.
Co ≥ 1 / (2π * 8Ω * 20 Hz) = 995 µF; use 1000 µF.
The high frequency pole is determined by the product of the
desired high frequency pole, fH, and the closed-loop gain, A
V. With a closed-loop gain of 1.4 and fH = 100 kHz, the
resulting GBWP = 140 kHz which is much smaller than the
LM4882 GBWP of 12.5Mhz. This figure displays that if a
designer has a need to design an amplifier with a higher
gain, the LM4882 can still be used without running into
bandwidth limitations.
(3)
For 250 mW of output power into an 8Ω load, the required
VOPEAK is 2 volts. A minimum supply rail of 4.55V results
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LM4882 MDA
AUDIO POWER AMPLIFIER WITH SHUTDOWN MODE
10003042
Die Layout (A - Step)
DIE/WAFER CHARACTERISTICS
Fabrication Attributes
General Die Information
Physical Die Identification
LM4882A
A
Bond Pad Opening Size (min)
Bond Pad Metalization
Passivation
95µm x 95µm
ALUMINUM
NITRIDE
Die Step
Physical Attributes
Wafer Diameter
Dise Size (Drawn)
150mm
Back Side Metal
Bare Back
GND
1016µm x 737µm
40mils x 29mils
406µm Nominal
137µm Nominal
Back Side Connection
Thickness
Min Pitch
Special Assembly Requirements:
Note: Actual die size is rounded to the nearest micron.
Die Bond Pad Coordinate Locations (A - Step)
(Referenced to die center, coordinates in µm) NC = No Connection
X/Y COORDINATES
PAD SIZE
SIGNAL NAME
PAD# NUMBER
X
Y
X
Y
SHUTDOWN
BYPASS
INPUT +
INPUT -
OUTPUT
VDD
1
2
3
4
5
6
7
-238
-376
-376
-376
376
376
376
237
186
-26
95
95
95
95
95
95
95
x
x
x
x
x
x
x
95
95
95
95
95
95
95
-237
-220
-76
GND
237
IN U.S.A
Tel #:
1 877 Dial Die 1 877 342 5343
1 207 541 6140
Fax:
IN EUROPE
Tel:
49 (0) 8141 351492 / 1495
49 (0) 8141 351470
Fax:
IN ASIA PACIFIC
Tel:
(852) 27371701
81 043 299 2308
IN JAPAN
Tel:
13
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Physical Dimensions inches (millimeters) unless otherwise noted
Order Number LM4882
NS Package Number M08A
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14
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
Order Number LM4882
NS Package Number MUA08A
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into the body, or (b) support or sustain life, and
whose failure to perform when properly used in
accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.
2. A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system, or to affect its
safety or effectiveness.
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Support Center
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Fax: +49 (0) 180-530 85 86
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