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Features
Ground Referenced Outputs
No Output Coupling Capacitors
16-Step Volume Control
High PSRR
Available in Space Saving LLP package
Low Power Shutdown Mode
Improved Click and Pop Suppression Eliminates Noises During Turn-on and Turn-off Transients
2.0V to 4.2V Operation
83mW Per Channel Into 16Ω
Selectable Shutdown Controls (Active High/Low)
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 eliminating 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 frequency
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.
Key Specification
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Improved PSRR at 217Hz
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67dB (typ)
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THD+N at 1kHz, 50mW
into 32Ω SE (3V)
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1.0% (typ)
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Single Supply Operation (VDD)
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2.0 to 4.2V
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Power Output at VDD = 3V,
RL = 16Ω, THD
≤ 1%
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83mW (typ)
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Shutdown Current
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0.01μA (typ)
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Applications
Portable MP3 Players
Mobile Phones
PDAs
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