LM49450 Datasheet, PDF (1/38 Pages) National Semiconductor (TI) – I2S Input, 2.5W/Channel, Low EMI, Stereo, Class D Audio Sub-System with Ground Referenced Headphone Amplifier, 3D Enhancement, and Headphone Sense

February 14, 2008
LM49450 
I²S Input, 2.5W/Channel, Low EMI, Stereo, Class D Audio
Sub-System with Ground Referenced Headphone
Amplifier, 3D Enhancement, and Headphone Sense
General Description
The LM49450 is a fully integrated audio subsystem designed
for portable media player applications. The LM49450 com-
bines a 24-bit I²S digital-to-analog converter (DAC), 2.5W/
channel stereo Class D speaker drivers, 36mW stereo ground
referenced headphone drivers, volume control, and
National’s unique 3D sound enhancement into a single de-
vice.
The filterless Class D amplifiers deliver 1.25W/channel into
an 8Ω load with <1% THD+N with a 5V supply. The LM49450
offers two logic selectable modulation schemes, fixed fre-
quency mode, and an EMI reducing spread spectrum mode.
The 36mW/channel headphone drivers feature National’s
ground referenced architecture that creates a ground-refer-
enced output from a single supply, eliminating the need for
bulky and expensive DC-blocking capacitors, saving space
and minimizing system cost. A headphone sense input (HPS)
automatically detects the presence of a headphone, and con-
figures the device accordingly.
The LM49450 stereo, 24-bit DAC supports a wide range of
sample rates (including 192kHz, 96kHz, 48kHz, and
44.1kHz). The digital audio signal path features better than
100dB SNR, and low 0.05% THD+N when measured at the
headphone outputs. The flexible 3-wire I²S interface supports
left or right justified audio data.
The LM49450 features separate 32-step volume control for
the headphones and speaker outputs. 3D enhancement,
mode selection, shutdown control, and volume are controlled
through an I²C compatible interface.
Output short circuit and thermal overload 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 LM49450 is
available in a space saving 32-pin LLP package.
Key Specifications
■ SNR at Headphone Output
■ Speaker Amplifier Efficiency
at 3.6V, 650mW/channel into 8Ω
■ Speaker Amplifier Efficiency
at 5V, 1.1W/channel into 8Ω
■ Quiescent Power Supply Current
Line Inputs:
 Speaker Mode at LSV_DD = 3.6V
 Headphone Mode at HPV_DD = 2.5V
102dBA (typ)
87% (typ)
80% (typ)
7.5mA (typ)
5.3mA (typ)
■ Output Power/Channel
 Speaker at LSV_DD = 5V:
R_L = 4Ω, THD+N ≤ 10%
R_L = 8Ω, THD+N ≤ 1%
 Headphone at HPV_DD = 2.5V:
R_L = 16Ω, THD+N ≤ 1%
R_L = 32Ω, THD+N ≤ 1%
■ PSRR at 1kHz
Speaker Mode
Headphone Mode
■ Shutdown current
2.5W (typ)
1.25W (typ)
34mW (typ)
36mW (typ)
67dB ( typ)
77dB (typ)
0.02μA (typ)
Features
■ ^{24–Bit Stereo DAC}
■ ^{Stereo Filterless Class D Operation}
■ ^{Selectable spread spectrum mode reduces EMI}
■ ^{Ground Referenced Headphone Amplifiers with 100dB}
SNR
■ ^{I2S Compatible Audio Interface}
■ ^{Audio Sample Rates up to 192kHz}
■ ^{National’s 3D Enhancement}
■ ^{32-step Digital Volume Control}
■ ^{I2C Compatible Control Interface}
■ ^{Headphone Sense Input}
■ ^{Stereo Analog Line Inputs}
■ ^{Output Short Circuit Protection}
■ ^{Thermal Overload Protection}
■ ^{Minimum external components}
■ ^{Click and Pop suppression}
■ ^{Micro-power shutdown}
■ ^{Available in space-saving 32 pin LLP package}
Applications
■ ^{Portable Media Players}
■ ^{Portable Navigation Devices}
■ ^{Multi-Media Monitors}
■ ^Laptops
■ ^{Portable Gaming Devices}
■ ^{Mobile Handsets}
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