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Stereo headphone amplifiers with low power consumption

Austria Microsystems has announced the AS3560 and AS3561 stereo headphone amplifiers for mobile phones, portable navigation devices, music/media players and any media device that uses headphones. These new 30mW headphone amplifiers continuously adjust the supply rails in response to the input signal, thus minimising power consumption as compared to traditional Class AB amplifiers. The AS3560 is a Class G amplifier while the AS3561 extends greater power savings with a Class H topology. Class G topology switches between three power rails, while 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 isless than 5µA. Audio performance is enhanced with more than 100dB SNR at 1 Vrms and THD of 0.02% at 16Ω.

The 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. The amplifiers are available in a 16-ball 1.6x1.6mm WL-CSP package. Both operate over a temperature range of -30 to +85 °C.