Uplink noise suppression & downlink SNR enhancement analog audio subsystem


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DSBGA (YZR) 36 12 mm² 3.475 x 3.499 open-in-new Find other Microphone preamplifiers


  • Noise cancellation for uplink and downlink without DSP-type artifacts, distortions or delays
  • Adapting AGC on ambient noise level & downlink signal strength for earpiece
  • Downlink adjustable noise-reducing high pass filter
  • E 2 S Class D Amplifier with ALC
  • Ground Referenced Headphone Outputs with Advanced Click Pop Suppression
  • Micro-power shutdown

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    The LM49155 is a fully integrated audio subsystem designed for portable handheld applications such as cellular phones. The LM49155 combines a Noise Suppression microphone amplifier, a 1.35W mono class D amplifier with ALC, class AB earpiece driver with AGC, a high efficiency, stereo, ground referenced headphone amplifier with click pop suppression and I 2C modes select and volume control.

    The LM49155 features analog fully differential input, and differential output microphone amplifier designed to reduce background acoustic noise, while delivering superb speech clarity in voice communication applications. Downlink SNR enhancement with an advanced acoustic AGC technology to adjust output levels.

    The LM49155 speaker amplifier features National’s unique output limiter that provides both a no-clip feature and speaker protection. The E 2S class D amplifier features a patented, ultra low EMI PWM architecture that significantly reduces RF emissions while preserving audio quality and efficiency. The headphone drivers feature National’s ground referenced architecture that creates a ground-referenced output from a single, low-voltage supply.

    The LM49155 is available in an ultra-small 36-bump micro SMD package (3.434mm x 3.459mm x 0.6mm).

    Notice: This document is not a full datasheet. For more information regarding this product or to order samples please contact your local National Semiconductor sales office or visit http://www.national.com/support/dir.html

    Key Specifications

    Uplink Far Field Noise Suppression  Electrical FFNSE at f = 1kHz 34dB (typ)
    Downlink SNR Enhancement Earpiece Amplifier
      Near-Field SNR Enhancement  Downlink SNRIE 6 to 18dB (typ) 16dB (typ)
    Class D Loudspeaker Amplifier RL = 15μH+8Ω+15μH
     POUT, THD+N %, VDD = 5.0V 1.35W (typ)
    Headphone Amplifier RL = 32Ω
     POUT, THD+N %, HPVDD = 1.8V 19mW (typ)

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    * Data sheet Uplink Noise Supp & Dwnlnk SNR Enhance Analog Audio Subsystm datasheet Jul. 21, 2010

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