奥地利微电子（ams）AS3400单路环境噪音消除（ANC）解决方案

kunluo · 发表于 2014-8-25 17:15:53

Austriamicrosystems公司的AS3400/10/30集成了环境噪音消除（ANC）功能的扬声器放大器，能降低本底环境噪音，从而提高了手持设备，耳机，语音通信设备等的音频质量。ANC处理的带宽10-2000Hz，噪音降低10-30dB，主要用于耳机，手持设备，手机，免提卡和语音通信设备。本文介绍了AS3400/10/30主要特性，反馈和正馈方框图，反馈应用案例电路图与差分正馈应用案例电路图。

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 background 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 configurations for best trade-off of noise cancellation, required filtering 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 handset 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.

AS3400/10/30主要特性：

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

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

function 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; <1μA quiescent

Extended PSRR for 217Hz

Interfaces

2-wire serial control mode & volume inputs

Calibration via Line-In or 2-wire serial interface

(patent pending)

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

AS3400/10/30应用：

The devices are ideal for Ear pieces, Headsets,

Hands-Free Kits, Mobile Phones, and Voice

Communicating Devices.

图1。AS3400反馈方框图

图2。AS3400前馈方框图

图3。AS3400前馈ANC方框图

图4。AS3430反馈应用案例电路图

图5。AS3430差分正馈应用案例电路图