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Audio amp subsystem simplifies designs

Santa Clara, Calif. — National Semiconductor Corp. today introduced the Boomer audio subsystem to simplify the development of full-bandwidth stereo and 3D sound in mobile phones and other battery-powered devices.

The LM4844 integrates 1.2-W stereo speaker amplifiers and headphone drivers, volume control, mixing, power management features and 3D sound enhancement. Boomer audio power amplifiers provide high-quality output power with a minimal number of external components, said Mike Polacek, vice president of National's Audio Products Group.

Operating on a 3.3-V supply, and featuring low shutdown current of 0.1 μA typical, National's LM4844 integrated stereo speaker drivers deliver 495 mW of output power per channel into an 8-Ω load, and the stereo headphone drivers deliver up 33 mW into a 32-Ω load. The subsystem is controlled through an I²C compatible interface that allows designers to utilize independent left-, right- and mono-volume controls.

The LM4844's output capacitor-less (OCL) headphone topology eliminates the need for external capacitors at the headphone outputs, saving board space, Polacek said. The OCL headphone topology also improves low frequency response and reduces pop and clicks on the headphone driver, Polacek said.

The LM4844's 3D enhancement improves stereo channel separation when the left and right speakers are too close together and solves problems that would otherwise arise from system size constraints or equipment limitations, Polacek said. In addition, the LM4844 routes and mixes the stereo and mono inputs into 10 distinct output modes which give designers flexibility to route and mix audio signals to either the stereo speakers or stereo headphones.

 
 
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Available now in a 30-bump micro SMD package that measures 2.5mm by 3mm, the LM4844 is priced at $2 each in 1,000-unit quantities. Click here for the LM4844 data sheet.

National Semiconductor , 1-800-272-9959, www.National.com.

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