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Stereo headphone amps minimise power consumption

Posted: 27 Aug 2010     Print Version  Bookmark and Share

Keywords:stereo  headphone  amplifiers  mobile  audio 

austriamicrosystems reveals the AS3560 and AS3561, two 30mW stereo headphone amplifiers that continuously adjust the supply rails in response to the input signal and minimise power consumption compared to traditional Class AB amplifiers. The amplifiers are targeted for mobile phones, portable navigation devices, music and media players and any media device that uses headphones.

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 minimise 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 5µA.

The company claims that the audio performance offers >100dB SNR at 1Vrms and THD of 0.02 per cent at 16Ω, 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 minimises 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 minimising 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 Rs.44.62 ($0.95) for the AS3560 and Rs.46.03 ($0.98) for the AS3561 for 1,000 piece quantities. Both operate over a temperature range of -30°C to +85°C.

- Paul Buckley
EE Times

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