Targeting mobile phones, portables, and other devices that use headphones, the Class G AS3560 and Class H AS3561 30-W stereo headphone amplifiers continuously adjust the supply rails in response to the input signal, which according to the company consumes less power than traditional Class AB amplifiers. Both devices use differential line inputs to minimize the effects of ground noise and EMI susceptibility, and also feature low quiescent current (1 mA) with both channels enabled.
The shutdown current is extremely low — less than 5 µA. The 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. Features include greater than 100 dB SNR at 1 Vrms and THD of 0.02% at 16 Ω.
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 I2 C bus allows volume control with 32 gain steps as well as independent channel control. Housing is in a 16-ball WL-CSP package, and the temperature range is –30° to 85°C. (Ea/1,000: AS3560, $0.95; AS3561, $0.98 — available now.)
austriamicrosystems , Unetrremstaetten , Austria
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