Chip puts active noise cancellation into bundled headphones

AMS is claiming up to 30dB of external noise attenuation over 20Hz-2kHz from its latest speaker driver chip.

AS3412 block diag - Chip puts active noise cancellation into bundled headphones

AS3412 opens up mass market opportunity for active noise cancellation, it is ideal for use in the bundled head-sets supplied with smartphones,” said the firm.

On-chip is proprietary analogue noise cancellation, combined with a speaker driver capable of delivering 2x34mW into a 32Ω load.

“Unlike more complex digital implementations, the AS3412 only requires a small number of supporting components, including a filter network composed of low-cost capacitors and resistors,” said AMS.

It operates from 1.6-1.8V, and is compatible with USB Type-C and Lightning inter-faces. Typical power consumption in normal feed-forward operation, with a 260µA load for twin microphones, is 11.5mW.

A novel inclusion is integrated depletion-mode (‘on’ with no power supply) mosfet switching which by-passes the chip’s electronics when power is removes, eliminating the need for electromechanical bypass switching – for example when the battery goes flat.

Claimed audio performance is 112.5dB signal-to-noise ratio, and total harmonic distortion and noise figure of less than 0.01%, at “a music output power” of 30mW, said AMS.

The package is 2.2 x 2.2 x 0.4mm, chip-scale.

“With the introduction of the AS3412, AMS is making it possible to fit active noise cancellation inside a traditional hands-free headset dongle, even in low-cost headsets,” said marketing manager Anna Wutke.

There is a development kit including a software GUI, firmware and simulation environment.

See the chip next at Electronica Shanghai.

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