LM4949_07 Datasheet, PDF (1/42 Pages) –

January 2007
LM4949 
Stereo Class D Audio Subsystem with OCL Headphone
Amplifier
General Description
The LM4949 is a fully integrated audio subsystem designed
for stereo cell phone applications. The LM4949 combines a
2.5W stereo Class D amplifier plus a separate 190mW stereo
headphone amplifier, volume control, and input mixer into a
single device. The filterless class D amplifiers deliver 1.19W/
channel into an 8Ω load with <1% THD+N from 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. Ad-
ditionally, the headphone amplifiers can be configured with
capacitively coupled (CC)loads, or used to drive an external
headphone amplifier. When configured for an external ampli-
fier, the V_DD/2 output (VOC) controls the external amplifier’s
shutdown input.
For improved noise immunity, the LM4949 features fully dif-
ferential left, right and mono inputs. The three inputs can be
mixed/multiplexed to either the speaker or headphone ampli-
fiers. The left and right inputs can be used as separate single-
ended inputs, mixing multiple stereo audio sources. The
mixer, volume control, and device mode select 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.
Key Specifications
■ Efficiency V_DD = 3.6V, 400mW
 into 8Ω
■ Efficiency V_DD = 5V, 1W into 8Ω
■ Quiescent Power Supply Current
  @ 3.6V
■ Power Output at V_DD = 5V
Speaker:
R_L = 4Ω, THD+N ≤ 1%
R_L = 8Ω, THD+N ≤ 1%
R_L = 4Ω, THD+N ≤ 10%
Headphone:
R_L = 16Ω, THD+N ≤ 1%
R_L = 32Ω, THD+N ≤ 1%
■ Shutdown Current
86.5%
87.4%
9.36mA
2W
1.19W
2.5W
153mW
89mW
0.1μA
Features
■ ^{Output Short Circuit Protection}
■ ^{Thermal Shutdown}
■ ^{Stereo filterless Class D operation}
■ ^{Selectable OCL/CC Headphone Drivers}
■ ^{RF Suppression}
■ ^{I2C Control Interface}
■ ^{32-step digital volume control}
■ ^{Independent Speaker and Headphone Gain Settings}
■ ^{Minimum external components}
■ ^{Click and Pop suppression}
■ ^{Micro-power shutdown}
■ ^{Available in space-saving 25 bump µSMD package}
Applications
■ ^{Mobile phones}
■ ^PDAs
■ ^Laptops
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