AS3400 AS3410 AS3430

Low Power Ambient Noise-Cancelling Sp eaker Driver

www.austriamicrosystems.com

Revision 0.2

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Product Brief

1 General Description

The AS3400/10/30 are speaker driver with Ambient

Noise Cancelling function for handsets, headphones or

ear pieces. It is intended to improve quality of e.g. music

listening, a phone conversation etc. by reducing back-

ground ambient noise.

The fully analog implementation allows the lowest power

consumption, lowest system BOM cost and most natural

received voice enhancement otherwise difficult to

achieve with DSP implementations. The device is

designed to be easily applied to existing architectures.

An internal OTP-ROM can be optionally used to store

the microphones gain calibration settings.

The AS3400/10/30 can be used in different configura-

tions for best trade-off of noise cancellation, required fil-

tering functions and mechanical designs.

The simpler feed-forward topology is used to effectively

reduce low frequency background noise. The feed-back

topology with either 1 or 2 filtering stages can be used to

reduce noise for a larger frequency range, and to even

implement transfer functions like speaker equalization,

Baxandall equalization, high/low shelving filter and to set

a predefined loop bandwidth.

The filter loop is optimized by the user for specific hand-

set electrical and mechanical designs by dimensioning

simple R, C components.

Most handset implementations will make use of a single

noise detecting microphone. Two microphones could be

used to allow for increased flexibility of their location in

the handset mechanical design. Using the bridged mode

allows to even drive high impedance headsets.

2 Key Features

Microphone Input

128 gain steps @0.375dB and MUTE with AGC

differential, low noise microphone amplifier

single ended or differential mode

improved supply for electret microphone

MIC gain OTP programmable

High Efficiency Headphone Amplifier

2x34mW, 0.1% THD @ 16Ω, 1.5V supply,

100dB SNR

bridged mode for e.g. 300Ω loads

click and pop less start-up and mode switching

Line Input

volume control via serial interface or volume pin

64 steps @ 0.75dB and MUTE, pop-free gain setting

single ended stereo or mono differential mode

ANC processing

feed-forward cancellation

feed-back cancellation with filter loop transfer func-

tion definable via simple RC components

simple in production SW calibration

12-30dB noise reduction (headset dependent)

10-2000Hz wide frequency active noise attenuation

(headset dependent)

Monitor Function

for assisted hearing, i.e. to monitor announcements

fixed (OTP prog.) ambient sound amplification to

compensate headphone passive attenuation

volume controlled ambient sound amplification

mixed with fixed (OTP prog.) attenuation of LineIn

Incremental Functions

ANC with or without music on the receiving path

improved dynamic range playback

OTP ROM for automatic trimming during production

(4 times programbable)

Performance Parameter

5/3.8mA @ 1.5V stereo/mono ANC; <1uA quiescent

extended PSRR for 217Hz

Interfaces

2 wire serial control mode & volume inputs

calibration via Line-In or 2-wire serial interface

single cell or fixed 1.0-1.8V supply with internal CP

Package

AS3400, AS3410 QFN24 [4x4mm] 0.5mm pitch

AS3430 QFN32 [5.x5mm] 0.5mm pitch

3 Applications

Ear pieces, Headsets, Hands-Free Kits, Mobile Phones,

Voice Communicating Devices