ICs drive ceramic and piezoelectric speakers

Three new Boomer audio amplifiers are billed as the industry's first single-chip devices to drive ceramic and piezoelectric speakers in portable applications.

Three new Boomer audio amplifiers from National Semiconductor are the industry's first single-chip devices to drive ceramic and piezoelectric speakers in portable applications.

These integrated chips allow manufacturers to create "credit-card-thin" handsets or add additional features to designs because they save space and reduce power consumption, enabling longer battery life and talk time.

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 4mm or greater thickness of traditional moving coil speakers, ceramic speakers are only 0.7mm thick.

They often weigh less than 1g and consume less than 5mW 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 cellphone, selected National's LM4802B and LM4961 speaker drivers for its new line of phones.

In addition to cellphone 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 is continuing to prove its leadership in complete audio solutions", said Mike Polacek, Vice President of National Semiconductor's Audio Group.

"Working closely together with industry leaders Panasonic Mobile Communications and speaker maker Taiyo Yuden in Japan has allowed us to take compelling breakthrough technology for ceramic speakers and bring it to market quickly".

"Ultimately, consumers will win when they buy thin Panasonic phones with Taiyo Yuden speakers and National's Boomer audio ICs".

National Semiconductor's LM4960, LM4961 and LM4802B single-chip devices integrate a boost convertor 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 12V peak-peak for ceramic speaker applications and the LM4960 delivers 24V peak-peak 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 convertor operating at a fixed frequency of 1.6MHz, to drive a dual audio power amplifier.

It delivers 24V peak-peak mono-BTL to a piezoelectric speaker with less than 1% THD+N while operating on a 3V 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 1000-unit quantities.

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