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PDF LM4671 Data sheet ( Hoja de datos )
| Número de pieza | LM4671 | |
| Descripción | Filterless High Efficiency 2.5W Switching Audio Amplifier | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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March 3, 2008
www.DataSheet4U.com
LM4671
Filterless High Efficiency 2.5W Switching Audio Amplifier
General Description
The LM4671 is a single supply, high efficiency 2.5W switching
audio amplifier. A low noise, filterless PWM architecture elim-
inates the output filter, reducing external component count,
board area consumption, system cost, and simplifying design.
The LM4671 is designed to meet the demands of mobile
phones and other portable communication devices. Operat-
ing on a single 5V supply, it is capable of driving a 4Ω speaker
load at a continuous average output of 2.1W with less than
1% THD+N. Its flexible power supply requirements allow op-
eration from 2.4V to 5.5V.
The LM4671 has high efficiency with speaker loads compared
to a typical Class AB amplifier. With a 3V supply driving an
8Ω speaker, the IC's efficiency for a 100mW power level is
80%, reaching 88% at 400mW output power.
The LM4671 features a low-power consumption shutdown
mode. Shutdown may be enabled by driving the Shutdown
pin to a logic low (GND).
The gain of the LM4671 is externally configurable which al-
lows independent gain control from multiple sources by sum-
ming the signals.
Key Specifications
■ Efficiency @ 3.6V, 100mW into
8Ω speaker
■ Efficiency @ 3.6V, 400mW into
8Ω speaker
■ Efficiency @ 5V, 1W into 8Ω
speaker
■ Quiescent current, 3.6V supply
■ Total shutdown power supply
current
■ Single supply range
80% (typ)
88% (typ)
86% (typ)
2.8mA (typ)
0.01µA (typ)
2.4V to 5.5V
Features
■ No output filter required for inductive loads
■ Externally configurable gain
■ Very fast turn on time: 17μs (typ)
■ Minimum external components
■ "Click and pop" suppression circuitry
■ Micro-power shutdown mode
■ Available in space-saving microSMD package
Applications
■ Mobile phones
■ PDAs
■ Portable electronic devices
Typical Application
201073j3
FIGURE 1. Typical Audio Amplifier Application Circuit
Boomer® is a registered trademark of National Semiconductor Corporation.
© 2008 National Semiconductor Corporation 201073
www.national.com
1 page  
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 conditiownswfowr w.DhaichtathSehdeeevitc4eUis.com
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 TJMAX, θJA, and the ambient temperature TA. The maximum
allowable power dissipation is PDMAX = (TJMAX–TA)/θJA or the number given in Absolute Maximum Ratings, whichever is lower. For the LM4671, TJMAX = 150°C.
The typical θJA is 220°C/W for the microSMD package.
Note 4: Human body model, 100pF discharged through a 1.5kΩ resistor.
Note 5: Machine Model, 220pF–240pF discharged through all pins.
Note 6: Typical specifications are specified at 25°C and represent the parametric norm.
Note 7: Tested limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
Note 8: Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis.
Note 9: Shutdown current is measured in a normal room environment. Exposure to direct sunlight will increase ISD by a maximum of 2µA. The Shutdown pin
should be driven as close as possible to GND for minimal shutdown current and to VDD for the best THD performance in PLAY mode. See the Application
Information section under SHUTDOWN FUNCTION for more information.
Note 10: The performance graphs were taken using the Audio Precision AUX-0025 Switching Amplifier measurement Filter in series with the LC filter on the
demo board.
External Components Description
(Figure 1)
Components
Functional Description
1. CS Supply bypass capacitor which provides power supply filtering. Refer to the Power Supply Bypassing section
for information concerning proper placement and selection of the supply bypass capacitor.
2. CI Input AC coupling capacitor which blocks the DC voltage at the amplifier's input terminals.
5 www.national.com
5 Page 
Ri3 = 1 / (1/Ri1 + 1/Ri2 + 1/Rin ...) (Ω)
(5)
The LM4671 may also use a combination of single-ended and
differential sources. A typical application with one single-end-
ed source and one differential source is shown in Figure 7.
Using the principle of superposition, thewewxtwer.nDaal tcaoSmhpeoent4eUn.tcom
values can be determined with the above equations corre-
sponding to the configuration.
FIGURE 2. Differential input configuration
201073i7
201073i8
FIGURE 3. Differential input configuration with input capacitors
11 www.national.com
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet LM4671.PDF ] | |
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