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Home » NEWEST Products » New by Category » Semiconductors » Amplifier ICs » AS342x Ambient Noise Cancellation Speaker Driver - ams
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AMS AS342x Ambient Noise Cancellation Speaker Driver

AMS AS342x Ambient Noise Cancellation Speaker Driver

AMS AS342x Ambient Noise Cancellation Speaker Driver is ideal for headsets, 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 microphone gain calibration settings as well as all application specific settings. The AS342x 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 frequencies typically up to 2-3kHz. The feed-back topology with either 1 or 2 filtering stages has it strengths especially at very low frequencies. The typical bandwidth for feedback system is from 20Hz up to 1kHz which is a little bit lower than with feed forward systems. The filter loop is determined by measurements, for each specific headset individually, and depends very much on mechanical designs. The gain and phase compensation filter network is implemented with cheap resistors and capacitors for lowest system costs. AS3422 features also an audio playback only mode which allows the user to easily switch between ANC on and off mode. In ANC off mode unused blocks are automatically switch off to guaranty lowest power consumption in each operating mode.

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:
    • 100dB SNR
    • 2x23mW, 0.1% THD @ 32W, 1.5V supply, Bridged mode for e.g. 300W loads
    • Click and pop less start-up and mode switching
  • Line Input:
    • Volume control via serial interface or push buttons
    • 64 steps @ 0.75dB and MUTE, pop-free gain setting
    • Fully differential stereo line inputs
  • ANC processing:
    • Feed-forward cancellation definable via simple RC components
    • Feed-back cancellation with filter loop transfer function
    • Simple in production SW calibration
    • 12-30dB noise reduction (headset dependent)
    • 10-3000Hz wide frequency active noise attenuation (headset

  • Monitor Function:
    • For assisted hearing, i.e. to monitor announcements headphone passive attenuation
    • Fixed (OTP prog.) ambient sound amplification to compensate
  • Incremental Functions:
    • ANC with or without music on the receiving path
    • Music Playback mode for lowest power consumption
    • OTP ROM for automatic trimming during production (4 times programmable)
  • Performance Parameter:
    • 7mA @ 1.5V stereo ANC; <1AA quiescent
    • Extended PSRR for 217Hz
    • Increased TDMA noise immunity
  • Interfaces:
    • 2-wire serial control mode & volume inputs
    • Calibration via Line-In or 2-wire serial interface
    • Fixed 1.0-1.8V supply with internal CP
AMS AS3421 Block Diagram
AMS AS3421 Block Diagram
AMS AS3422 Block Diagram
AMS AS3421 Block Diagram
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