News and New Products

Low-power audio codec incorporates Class D loudspeaker amplifier

By Paul Rako, Technical Editor -- EDN, 4/2/2009

National Semiconductor recently announced the low-power LM49352 audio codec (compressor/decompressor) for handheld consumer electronics. The part includes an audio codec with ground-referenced headphone amplifiers, Class D loudspeaker outputs, and an audio DSP. The loudspeaker delivers 93% efficiency at 970 mW from a 4.2V supply. The headphone amplifier offers 18 mW MP3 playback to extend battery life. Applications include smartphones, full-featured phones, portable gaming devices, and portable GPS (global-positioning-system) devices.

The device integrates a charge pump to increase power to the loudspeakers. It also includes a DAC, which achieves 103-dB SNR (signal-to-noise ratio), and an ADC, which provides 97-dB SNR. The part can play back audio with 96-kHz sampling rates and can record audio at 48 kHz. It also incorporates dual-stereo, five-band parametric equalizers; ALC (average-level control); and limiter and compressor functions on both the DAC and the ADC signal paths. The codec also features differential-microphone inputs to minimize noise, crosstalk, and RF susceptibility. The ADC has a wind-noise filter that can operate in voice- or high-fidelity-recording modes.

The LM49352 comes in a 36-bump micro SMD package and sells for $7.55 (1000) and is available for sampling, along with evaluation boards.