Audio amplifiers cut power consumption

Santa Clara, Calif. — National Semiconductor Corp. expanded its ceramic speaker driver family today with two Boomer audio power amplifiers in tiny packages that are said to provide high capacitive loads for portable applications like cell phones, smartphones, and notebook computers.

“The LM4962 and LM4953 integrated drivers allow manufacturers to create credit-card-thin handsets or add additional features to designs because the chips save space and reduce power consumption,” said Mike Polacek, vice president of National Semiconductor's Audio group.

The LM4962 ceramic speaker driver saves designers 80 percent board space over National's previous generation, reducing the integrated circuit size from 25-mm squared to 5-mm squared. To address the high voltage needs of ceramic speaker's capacitive loads, the single chip integrates a boost converter with an audio power amplifier for mono ceramic speaker applications. For stereo applications, the boost converter of the LM4962 also can drive a second external audio high-voltage amplifier such as National's LM4951.

The LM4953 ceramic speaker driver is National's first audio amplifier to use a charge pump to drive the ceramic speaker, Polacek said. The LM4953 requires only eight external components — eliminating the need for an expensive voltage regulator and large inductor, he added.

The LM4962 ceramic speaker driver provides 15-volt peak to peak across a bridge-tied-load (BTL) with less than 1 percent total harmonic distortion plus noise (THD+N) from a 3.2 V DC power supply. In addition, the LM4962 features overcurrent protection for the boost converter and overvoltage protection. The DC/DC converter features a soft-start function. The LM4962 includes a low-power mode for earpieces and a high-power mode to drive the ringtones and handsfree speakers.

The LM4953 audio amplifier and integrated charge pump, in a 3 x 4 mm package, allow a voltage boost from a 3.6-V supply, delivering 12.6-V peak to peak across a 2 microfarad +30-ohm BTL with less than 1 percent THD+N.

The LM4962, available in a 28-bump thin micro SMD package, is priced at $2.50. Click here for the LM4962 data sheet. The LM4953 is priced at $1.85 in a 14-pin pullback LLP package. Click here for the LM4953 data sheet. All prices are in 1,000-unit quantities. These chips are offered in standard or lead-free packages.

National Semiconductor , 1-800-272-9959,

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