Audio subsystems have expanded feature sets

National Semiconductor has launched two Boomer audio subsystems that provide a wide variety of features for cellular phones and portable applications.

National Semiconductor has launched two Boomer audio subsystems that provide a wide variety of features for cellular phones and portable applications.

The LM4859 compact subsystem integrates the audio amplifiers, volume control, mixer, power management control, 3D sound enhancement and I2C control all into a single, space-saving package.

The full-featured LM4931 contains a stereo I2S DAC, on-board phase-locked-loop (PLL), a voice band codec, stereo headphone amplifier, Class D mono speaker amplifier, microphone pre-amplifier and side-tone generator, all with an I2C or SPI digital control interface.

I2C/SPI control allows selection of a variety of operating modes, volume control, and other performance functions.

"National's LM4859 and LM4931 integrated audio subsystems provide everything our customers need," said Roland Dorn, marketing manager for National Semiconductor's audio products group in Europe.

"These audio subsystems give customers a huge feature set in a very compact space.

By integrating all of the features that a customer might need into a single package, the LM4859 and LM4931 provide space and system cost savings without sacrificing performance.

These subsystems give customers the outstanding audio clarity and functionality that National's Boomer product family is known for." Incredible integration with minimal software required National's LM4859 is an integrated audio subsystem that operates on a 2.7-5.5V supply.

It combines a stereo speaker amplifier that delivers 495mW per channel into an 8 Ohm load, and a stereo headphone amplifier that delivers 25mW per channel into a 32 Ohm load with a 3.3V power supply.

In addition, the LM4859 routes and mixes the stereo and mono inputs into 16 distinct output modes using a simple I2C compatible interface.

Other features include an ultra-low current shutdown mode and thermal shutdown protection.

National's LM4931 is an integrated audio subsystem that supports voice and digital audio functions.

The full range I2S music path features a signal-to-noise ratio of 86dB with an 18-bit, 48kHz input.

The high efficiency Class D speaker amplifier delivers 470mW into 8 Ohms and the headphone amplifier delivers 26mW root means square (RMS) to a 32 Ohm single-ended stereo load with less than one percent total harmonic distortion plus noise (THD+N) with a power supply of 3.3V.

Additionally, the LM4931 has advanced circuitry to reduce power consumption and controller overhead, and to eliminate pop and click noise.

Unlike hard to use audio codecs that require sophisticated software development for operation and control, both the LM4931 and LM4859 use a standard I2C or SPI compatible interface.

Simple I2C or SPI commands are used to set one of the operating modes and volume level for any given audio amplifier.

The operating modes are predetermined to cover all of the functional needs required in portable applications.

The LM4931 has 10 preset operating modes, while the LM4859 has extra modes for the 3D feature for a total of 16.

These modes not only make the devices easy to use but also allow the user to turn off unused amplifiers to optimize system power management.

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