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National’s Boomer speaker drivers promote credit-card thin handset designs

Santa Clara, Calif. — Today National Semiconductor Corp. unveiled a new trio of Boomer audio amplifiers that it says will result in “credit-card-thin” handsets and reduced power consumption.

National Semiconductor's LM4960, LM4961 and LM4802B are the industry's first integrated single-chip devices to drive ceramic and piezoelectric speakers in portable applications, according to the company. Ceramic and piezoelectric speakers are dramatically different from conventional moving coil speakers. They act as a capacitive rather than a resistive load and require much more voltage than current. In comparison to the 4-mm or greater thickness of traditional moving coil speakers, ceramic speakers are only 0.7-mm thick. They often weigh less than one gram and consume less than 5 mW of power. More information on these speaker types is available in National's Audio Education Series eBooks at audio.national.com.

Japan's Panasonic Mobile Communications, the first company in the industry to design a ceramic speaker into a cell phone, selected National's LM4802B and LM4961speaker drivers for their new line of phones. In addition to cell phone applications, National's LM4802B, LM4960 and LM4961 speaker drivers can also be designed into space-constrained portable applications such as personal digital assistants (PDAs), smartphones, notebook computers and other small handheld devices.

National Semiconductor's LM4960, LM4961 and LM4802B single-chip devices integrate a boost converter with an audio power amplifier, replacing the need for expensive voltage regulators and other external components and freeing up space in designs. The LM4802B and LM4961 audio speaker drivers deliver 12 Vp/p for ceramic speaker applications and the LM4960 delivers 24 Vp/p for piezoelectric speakers.

These amplifiers feature a low-power consumption shutdown mode and an internal thermal shutdown protection mechanism. In addition, they contain advanced “pop and click” circuitry to eliminate noises that typically occur during turn-on and turn-off transitions. All three speaker drivers allow the flexibility of running a handset at a low voltage, increasing talk time in cellular applications. National's new amplifiers provide additional benefits such as reduced component count and electromagnetic interference and noise, as well as increased space savings and performance for customers.

The LM4960 is designed for piezoelectric speakers. It integrates a switching regulator, a current-mode boost converter operating at a fixed frequency of 1.6 MHz, to drive a dual audio power amplifier. It delivers 24 Vp/p mono-bridge-tied load (BTL) to a piezoelectric speaker with less than 1% total harmonic distortion plus noise (THD+N) while operating on a 3 V-power supply.

The LM4961 for ceramic speakers includes added battery savings, with a low-power mode for earpieces and a high-power mode to drive the ringtones and hands-free speakers.

Available now in 28-pin pullback LLP packages, the LM4802B is priced at $1.65 and the LM4961 is priced at $2.10. The LM4960 is available now in a 28-pin non-pullback LLP package and is priced at $2.50. All pricing is in 1,000-unit quantities.

Click here for the LM4802B data sheet.

Click here for the LM4960 data sheet.

Click here for the LM4961 data sheet.

For more information, please call (408) 721-5000 or visit: www.national.com

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