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National Semiconductor Corporation (NS) announced that its new Boomer® audio subsystem includes National Semiconductor's programmable 3D audio enhancements in addition to its built-in 2.2W stereo Class D audio amplifier. Automatic headphone detection and 155mW no output capacitor stereo headphone amplifier. This subsystem is best suited for portable media players, portable DVD players and multimedia phones.National's highly integrated LM49270 filterless audio subsystem features high output power and a built-in flexible I2C-compatible serial interface that allows the circuit to quickly adjust its functionality to support different applications. For example, this subsystem has a headphone detection function that automatically switches between the speaker and headset modes. The stereo headphone amplifier of the LM49270 audio subsystem can be configured with either capacitor coupling mode or output capacitor mode to meet different design requirements. If the system design engineer chooses a structure without an output capacitor, there is no need to add a bulky but expensive output coupling capacitor like a conventional headphone amplifier.
The audio subsystem also has volume control for the headphones and speakers. The volume is divided into 32 steps and can be adjusted by controlling the output power. With headphone mode, the LM49270 audio subsystem has a quiescent current of only 4.7mA, ensuring extended battery life, and the subsystem can utilize a 5V power supply with 2.2W of power to drive a 4 Ohm load, total harmonic distortion and noise. Not more than 10%.
Other key features and benefits
· The headphone sensing circuit can use its detection function to determine if the headset is connected. Once the headset is connected, the subsystem will be reconfigured to support the headset mode.
· There are multiple modes to choose from and the volume can be controlled via the built-in I2C compatible interface
· Independent speaker and headphone volume control
·Output short circuit and overheat protection
·Switch / switching noise suppression
·Micropower shutdown
The LM49270 is available in a 28-pin LLP® package and is priced at $2.45 each in 1,000-unit quantities.
PMR/FRS Two-Way Radio,Professional Two-Way Radio Co., Ltd. , http://www.chtwowayradio.com