Stereo headphone amplifiers for media devices

The 30mW headphone amplifiers continuously adjust the supply rails in response to the input signal, therefore minimising power consumption as compared with traditional Class AB amplifiers.

The AS3560 is a Class G amplifier while the AS3561 features 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 less than 5uA.

Audio performance remains good with >100dB SNR at 1Vrms and THD of 0.02 per cent at 16ohm, making the AS3560/AS3561 ideal devices where power consumption and audio performance are important.

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.

The AS3560 and AS3561 are available in a 16-ball 1.6 x 1.6mm WL-CSP package.

Both operate over a temperature range of -30C to +85C.