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Stereo headphone amps adjust supply rails

Posted: 25 Aug 2010 ?? ?Print Version ?Bookmark and Share

Keywords:stereo? headphone? amplifiers? mobile? audio?

Austriamicrosystems launches two stereo headphone amplifiers for mobile phones, portable navigation devices, music and media players and any media device that uses headphones.

The new 30mW amps continuously adjust the supply rails in response to the input signal and minimize power consumption compared to traditional Class AB amplifiers.

The AS3560 is a Class G amplifier while the AS3561 extends the power savings even more with a Class H topology. Class G topology switches between three power rails, while the Class H adapts the power rail to whatever power is needed to drive the headphone volume. Both devices use differential line inputs to minimize the effects of ground noise and EMI susceptibility, and also feature low quiescent current of 1mA with both channels enabled. The shutdown current is extremely low at less than 5?A.

The company claims the audio performance offers >100 dB SNR @ 1Vrms and THD of 0.02 percent at 16?, making the AS3560/AS3561 the best such devices available for power consumption and audio performance. The integrated charge pump generates a symmetric negative supply for true ground output signal levels, which saves space and minimizes system cost by eliminating the need for bulky and expensive DC blocking capacitors. An I2C bus allows volume control with 32 gain steps as well as independent channel control.

"Class G gives you all the benefits of a linear headphone driver in terms of sound quality, while minimizing the power loss", commented Oliver Jones, austriamicrosystems' Marketing Manager for Audio products. "This topology is without doubt the most efficient way to drive a headphone for cost vs. performance. But Class H goes even further, squeezing every last minute out of the battery."

The AS3560 and AS3561 are available in a 16-ball 1.6mm x 1.6mm WL-CSP package and are priced at $0.95 for the AS3560 and $0.98 for the AS3561 for 1,000 piece quantities. Both operate over a temperature range of -30C to +85C.

- Paul Buckley
EE Times

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