LM49270 Datasheet, PDF (1/24 Pages) Texas Instruments – Filterless 2.2W Stereo Class D Audio Subsystem with OCL Headphone Amplifier, 3D Enhancement, and Headphone Sense

December 2006
LM49270 
Filterless 2.2W Stereo Class D Audio Subsystem with OCL
Headphone Amplifier, 3D Enhancement, and Headphone
Sense
General Description
The LM49270 is a fully integrated audio subsystem designed
for stereo multimedia applications. The LM49270 combines a
2.2W stereo Class D amplifier with a 155mW stereo head-
phone amplifier, volume control, headphone sense, and
National’s unique 3D sound enhancement into a single de-
vice. The LM49270 uses flexible I²C control interface for
multiple application requirements.
The filterless stereo class D amplifiers delivers 2.2W/channel
into a 4Ω load with less than 10% THD+N with a 5V supply.
The headphone amplifier features National’s Output Capaci-
tor-less (OCL) architecture that eliminates the output coupling
capacitors required by traditional headphone amplifiers.
The IC features a headphone sense input (HPS) that auto-
matically detects the presence of a headphone and config-
ures the device accordingly. The LM49270 can automatically
switch from OCL headphone output to a line driver output. If
the VOC pin is pulled to GND, the VOC amplifier is disabled
and the VOC pin is internally set to GND. This feature allows
the LM49270 to be used as a line driver in OCL mode without
a GND conflict on the headphone jack sleeve. Additionally,
the headphone amplifier can be configured as capacitively
coupled (CC).
The LM49270 features a 32 step volume control for the head-
phone and stereo outputs. The device mode select and vol-
ume are controlled through an I²C compatible interface.
Output short circuit and thermal shutdown protection prevent
the device from being damaged during fault conditions. Su-
perior click and pop suppression eliminates audible transients
on power-up/down and during shutdown. The LM49270 is
available in a space saving 28-pin, 5x5mm LLP package.
Key Specifications
■ Stereo Class D Amplifier Efficiency:
 V_DD = 3.3V, 450mW/Ch into 8Ω
 V_DD = 5V, 1W/Ch into 8Ω
■ Quiescent Power Supply Current, V_DD = 3.3V
 Speaker Mode
 Headphone Mode (OCL)
■ Power Output/Channel, V_DD = 5V
 Class D Speaker amplifier:
R_L = 4Ω, THD+N = ≤ 10%
R_L = 8Ω, THD+N = ≤ 1%
 Headphone amplifier:
R_L = 16Ω, THD+N = ≤ 1%
R_L = 32Ω, THD+N = ≤ 1%
■ Shutdown current
84%
84%
5.5mA
4mA
2.2W
1.06W
155mW
90mW
0.02μA
Features
■ ^{Stereo filterless Class D amplifier}
■ ^{Selectable OCL/CC headphone amplifier}
■ ^{Headphone sense ability}
■ ^{National’s 3D Enhancement}
■ ^{RF suppression}
■ ^{I2C control interface}
■ ^{32-step digital volume control}
■ ^{6 Operating Modes}
■ ^{Output short circuit protection and thermal shutdown}
protection
■ ^{Minimum external components}
■ ^{Click and Pop suppression}
■ ^{Micro-power shutdown}
■ ^{Independent speaker and headphone volume controls}
■ ^{Available in space-saving 28 pin LLP package}
Applications
■ ^{Portable DVD players}
■ ^{Smart phones}
■ ^PDAs
■ ^Laptops
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