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National Semiconductor Corporation (NYSE: NSM) announced the launch of three Boomer® audio amplifier chips for portable systems. These three chips are the industry's first single-chip audio amplifiers that can drive ceramic and piezoelectric speakers. With these highly integrated amplifier chips, manufacturers can develop "thin credit card"-like mobile phones, and add more new features to the system design, because these chips are small in size and consume very little power. Helps extend the battery life and talk time of your phone.Ceramic and piezoelectric speakers are functionally different from traditional moving coil speakers. The former is functionally considered a capacitive load rather than a resistive load, and the required voltage is much higher than the current. Conventional moving coil speakers typically have a thickness of 4mm or more, compared to 0.7mm thick ceramic speakers, and often weigh less than one gram and consume no more than 5mW. A detailed description of this type of speaker is available on National's audio.national.com/CHS page. For more information on this, see the Audio Education Series eBook on this page. Column.
Japan's Panasonic Mobile Communications has successfully designed a mobile phone with ceramic speakers, the first company in the industry to launch the phone, and this new line of phones is using National's LM4802B and LM4961 speaker drivers. In addition to mobile phones, National's LM4802B, LM4960, and LM4961 speaker drivers are also ideal for ultra-thin portable electronics such as personal digital assistants, smart phones, notebooks, and Other handheld electronic devices.
National's LM4960, LM4961, and LM4802B single-chip speaker drivers integrate boost converters and audio power amplifiers, eliminating the need for expensive regulators and other external components to save more board space. The LM4802B and LM4961 audio speaker drivers provide a peak output voltage of 12 volts (V) for the ceramic squeaker, while the LM4960 provides a 24 volt peak output voltage for the enamel soup.
In addition to the low-power shutdown mode and internal thermal shutdown protection, these amplifiers also include advanced circuitry that suppresses switching noise, eliminating the noise that often occurs when switching between system switches. These three speaker drivers offer a high degree of flexibility to ensure that the phone operates at very low voltages to extend the talk time of the phone. National Semiconductor's new amplifiers have other advantages, such as reducing the number of components required, generating less electromagnetic interference and noise, saving more board space and further improving system performance.
The LM4960 is a driver designed for piezoelectric speakers. The built-in switching regulator is a current mode boost converter that operates at a fixed frequency of 1.6MHz and can drive dual output audio power amplifiers. With a 3-volt power supply, the chip can input a 24-volt mono bridged peak-to-peak output voltage into a piezo speaker with less than 1% total harmonic distortion and noise (THD+D).
Designed specifically for ceramic speakers, the LM4961 chip saves more power, and features a low-power mode for headphones and a high-power mode designed to drive ringtones and speakerphones.
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