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National Semi’s Class D boomer audio amps conserve space and extend battery life

Santa Clara, Calif. — National Semiconductor Corp. today introduced two new high-efficiency Class D audio amplifiers that eliminate external parts, enabling smaller footprint devices and simplifying designs.

These audio amplifiers are housed in micro SMD packages and feature externally configurable gain for space savings and flexibility in design. Additionally, they provide low power consumption shutdown mode for extended battery life. Applications include cellular phones, PDAs and other portable devices.

National Semiconductor's LM4670 (3 W) and LM4671 ( 2.5 W) fully integrated single-supply, high-efficiency switching audio amplifiers provide innovative modulation schemes that eliminate the output filter used with typical switching amplifiers, said Mike Polacek, vice president of National Semiconductor's Audio group. Doing so, reduces external component count, simplifies circuit design and reduces board area, Polacek said. The LM4670 processes analog inputs with a delta-sigma modulation technique that lowers output noise and total harmonic distortion (THD).

Due to its high output power, the LM4670 is optimized for ultra-high-power push-to-talk, push-to-talk over cellular (PoC) and hands-free use. The LM4671 processes analog inputs with a pulse width modulation technique that results in lower output noise, making it suitable for earpiece/receiver applications, as well as normal high-power ringer and hands-free operation.

Operating on a single 5 V supply, the LM4670 and LM4671 are capable of driving a 4Ω speaker load at a continuous average output of 2.3 W, with less than one percent THD plus noise (THD+N). Flexible power supply requirements of these parts allow operation from 2.4 V to 5.5 V. With a 3.6 V supply driving an 8Ω speaker, the amplifier's efficiency is 88 percent at 600 mW output power.

Available now in 9-bump micro SMD packages, the LM4670 and LM4671 are priced at 48 cents in 1,000-unit quantities. Click here for the LM4670 data sheet. Click here for the LM4671 data sheet.

National Semiconductor , 1-408-721-5000, www.national.com.

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