LM4681 Datasheet, PDF (1/19 Pages) National Semiconductor (TI) – 10 Watt Stereo CLASS D Audio Power Amplifier with Stereo Headphone Amplifier and I2C/SPI Volume Control

March 2006
LM4681
10 Watt Stereo CLASS D Audio Power Amplifier with
Stereo Headphone Amplifier and I²C/SPI Volume Control
General Description
The LM4681 is a fully integrated single supply, CLASS D
audio power amplifier solution. The LM4681 utilizes a pro-
prietary balanced pulse-width modulation technique that low-
ers output noise and THD and improves PSRR when com-
pared to conventional pulse width modulators.
The LM4681 also features a stereo headphone amplifier that
delivers 80mW into a 32Ω headset with less than 0.5% THD.
The LM4681’s I²C/SPI (selectable) volume control has a
+30dB to –48dB range when speakers are driven and a
range of +13dB to –65dB when headphones are connected.
All amplifiers are protected by thermal shutdown. Addition-
ally, the high efficiency power amplifiers have output current
limit.
With a 8Ω load, the IC’s efficiency for a 6W power level is
85%. The IC features click and pop reduction circuitry that
minimizes audible popping during device turn-on and turn-
off. The LM4681 is available in a 48-lead LLP package, ideal
for portable and desktop computer applications.
Key Specifications
n P_O at THD+N =10%, A_V = 30dB, V_DD = 14V 10W (typ)
n THD+N at 1kHz at 1W into 8Ω (Power Amp) 0.43% (typ)
n Efficiency at 7W into 8Ω
85% (min)
n Total quiescent power supply current
50mA (typ)
n THD+N 1kHz, 20mW, 32Ω (Headphone) 0.02% (typ)
n Single supply range
9.0V to 15.5V
Features
n Pulse-width modulator.
n I²C/SPI (selectable) volume control
n Stereo headphone amplifier.
n “Click and pop” suppression circuitry.
n Micropower shutdown mode.
n 48 lead LLP package (No heatsink required).
Applications
n Flat Panel Displays
n Televisions
n Multimedia Monitors
Block Diagram
Block Diagram for LM4681
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