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PDF LM4981 Data sheet ( Hoja de datos )
| Número de pieza | LM4981 | |
| Descripción | 80mW Stereo Headphone Amplifier | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LM4981 (archivo pdf) en la parte inferior de esta página. Total 18 Páginas | ||
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www.DataSheet4U.com
November 2005
LM4981
Ground-Referenced, 80mW Stereo Headphone Amplifier
with Digital Volume Control
General Description
The LM4981 is a stereo, ground-referenced, output
capacitor-less headphone amplifier capable of delivering
83mW of continuous average power into a 16Ω load with
less than 1% THD+N while operating from a single 3V
supply.
The LM4981 features a new circuit technology that utilizes a
charge pump to generate a negative reference voltage. This
allows the outputs to be biased about ground, thereby elimi-
nating output-coupling capacitors typically used with normal
single-ended loads.
The LM4981 provides high quality audio reproduction with
minimal external components. A ground referenced output
eliminates the output coupling capacitors typically required
to drive single-ended loads such as headphones. The
ground reference architecture reduces components count,
cost and board space consumption, making the LM4981
ideal for handheld MP3 players, mobile phones and other
portable equipment where board space is at a premium.
Eliminating the output capacitors also improves low fre-
quency response.
The LM4981 operates from a single 2.0V – 4.2V supply, and
features a 2-wire, up/down volume control that sets the gain
of the amplifier between -33dB to +12dB in 16 discrete
steps. Selectable (active high/low) low power shutdown
mode provides flexible shutdown control. Superior click and
pop suppression eliminates audible transients during
start-up and shutdown.
The LM4981 features an Automatic Standby Mode circuitry
(patent pending). In the absence of an input signal, after
approximately 12 seconds, the LM4981 goes into low cur-
rent standby mode. The LM4981 recovers into full power
operating mode immediately after a signal is applied to either
the left or right input pins. This feature saves power supply
current in battery operated applications.
Key Specifications
j Improved PSRR at 217Hz
j THD+N at 1kHz, 50mW
into 32Ω SE (3V)
j Single Supply Operation (VDD)
j Power Output at VDD = 3V,
RL = 16Ω, THD ≤ 1%
j Shutdown Current
67dB (typ)
1.0% (typ)
2.0 to 4.2V
83mW (typ)
0.01µA (typ)
Features
n Ground Referenced Outputs
n No Output Coupling Capacitors
n 16-Step Volume Control
n Auto-Standby Mode
n High PSRR
n Available in Space Saving LLP package
n Low Power Shutdown Mode
n Improved Click and Pop Suppression Eliminates Noises
During Turn-on and Turn-off Transients
n 2.0V to 4.2V Operation
n 83mW Per Channel Into 16Ω
n Selectable Shutdown Controls (Active High/Low)
Applications
n Portable MP3 Players
n Mobile Phones
n PDAs
Boomer® is a registered trademark of National Semiconductor Corporation.
© 2005 National Semiconductor Corporation DS201473
www.national.com
1 page  
Electrical Characteristics VDD = 3V (Notes 1, 2) (Continued)
Note 1: All voltages are measured with respect to the GND pin unless other wise 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 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 LM4917, see power
derating currents for more information.
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 parametric norm.
Note 7: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).
5 www.national.com
5 Page 
Typical Performance Characteristics (Continued)
Power Dissipation vs Output Power
RL = 32Ω, VDD = 3V
PSRR vs Frequency
VDD = 3V, RL = 32Ω
Vripple = 200mVp-p
20147382
20147383
11 www.national.com
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet LM4981.PDF ] | |
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