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National unveils two new amps

Posted: 23 Dec 2005 ?? ?Print Version ?Bookmark and Share

Keywords:National Semiconductor? Boomer? audio amplifier? LM4673? LM4673?

National's audio amplifier

National Semiconductor Corp. introduced a Boomer mono Class D audio amplifier in one of the industry's smallest micro SMD package, as well as a high-power stereo Class D amplifier. Both amps provide high-quality output power with a minimal number of external components for cellphones, smart phones and portable audio devices such as DVD players and gaming devices.

"National's Class D audio amplifier portfolio continues to meet our customers' design requirements for great audio performance in small, low-power, low-heat portable applications," said Mike Polacek, VP of National's Audio Group. "Our new LM4673 mono Class D amplifier comes in a tiny, 0.4mm-pitch micro SMD package to save space in manufacturers' designs. The stereo LM4674 Class D amplifier also provides great board-space efficiency for stereo applications."

The LM4673 is a fully differential, single-supply, filter-less, 2.5W Class D switching audio amplifier in a 1.4-by-1.4mm, 0.4mm-pitch micro SMD package. This package, which uses little space on the PCB, facilitates easier layout in small spaces. Consuming less power than any similar Class D audio amplifier available today, the LM4673 has a typical quiescent current of 2.1mA at a 3.6V supply, enabling longer talk times in mobile phones and more listening time for portable audio devices.

The LM4674 is a filterless, 2.4W stereo Class D audio power amplifier available in a 2-by-2mm, 0.5mm-pitch package. The chip also has a typical quiescent current of 4mA at a 3.6V supply for power savings.

Cuts external component count
Both the LM4673 and LM4674 audio amplifiers employ a low-noise, filter-less pulse-width modulation architecture that eliminates output filters, reducing external component count, saving space on the board layout, lowering system cost and simplifying the circuit design. The flexible power supply requirements of these parts allow operation from 2.4V to 5.5V.

Both of these Class D amplifiers have high efficiency with speaker loads compared to typical Class AB amplifiers. Each product features a low-power shutdown mode and internal, advanced "pop and click" circuitry that eliminates output transients which would otherwise occur during power or shutdown cycles. The gain of the LM4673 is externally configurable to allow the user to connect different multiple inputs while optimizing the gain for each source.

Operating on a single 5V supply, the LM4673 is capable of driving a 4? speaker load at a continuous average output of 2.5W with less than one percent total harmonic distortion plus noise (THD+N). In addition to its low quiescent current, the LM4673 offers a power supply rejection radio (PSRR) of 78dB at 217Hz, a common-mode rejection ratio (CMRR) of 70dB and a signal-to-noise ratio of 97dB. It also has a typical fast turn-on time of 17?s.

The LM4674 delivers 2.4W per channel of continuous output power to a 4? load with 10 percent THD+N. The chip features independent left and right shutdown controls to maximize power savings in mixed mono and stereo applications. And to give designers flexibility, the LM4674 has four gain settings of 6-, 12-, 18- and 24dB. The chip also has a PSRR of 75db at 217Hz.

Already available, the LM4673 is priced at 90 cents in a Pb-free, 9-bump micro SMD package. The LM4674 is offered in a standard or Pb-free, 16-bump micro SMD package and is priced at $1.50. Both prices are for 1,000-unit quantities.

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Related Datasheets
Part Number Description Category
? LM4673 Filterless, 2.65W, Mono, Class D Audio Power Amplifier from the PowerWise? Family Passives - Filters, Oscillators and Resonators



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