NS 公司的LM49155 是高度集成的PowerWise音频子系统，集成了噪音抑制麦克风放大器，1.35W单声道带ALC的D类放大器，带AGC的AB类耳机驱动器，带开关机声抑制的高效立体声参考地耳机放大器以及I2C模式选择和音量控制。主要用于手机和手提电子设备。本文介绍了LM49155主要指标，简化方框图以及典型应用电路。Uplink Noise Suppression & Downlink SNR Enhancement AnalogAudio SubsystemThe LM49155 is a fully integrated audio subsystem designed forportable handheld applications such as cellular phones. The LM49155combines a Noise Suppression microphone amplifier, a 1.35W monoclass D amplifier with ALC, class AB earpiece driver with AGC, ahigh efficiency, stereo, ground referenced headphone amplifier withclick pop suppression and I2C modes select and volume control.The LM49155 features analog fully differential input, anddifferential output microphone amplifier designed to reducebackground acoustic noise, while delivering superb speech clarityin voice communication applications. Downlink SNR enhancement withan advanced acoustic AGC technology to adjust output levels.The LM49155 speaker amplifier features National’s unique outputlimiter that provides both a no-clip feature and speakerprotection. The E2S class D amplifier features a patented, ultralow EMI PWM architecture that significantly reduces RF emissionswhile preserving audio quality and efficiency. The headphonedrivers feature National’s ground referenced architecture thatcreates a ground-referenced output from a single, low-voltagesupply.The LM49155 is available in an ultra-small 36-bump micro SMDpackage (3.434mm x 3.459mm x 0.6mm).LM49155主要指标：■ Uplink Far Field Noise Suppression Electrical FFNSE at f =1kHz 34dB (typ)■ Downlink SNR Enhancement Earpiece AmplifierNear-Field SNR Enhancement 6 to 18dB(typ)DownlinkSNRIE 16dB (typ)■ Class D Loudspeaker Amplifier RL = 15μH+8Ω+15μHPOUT, THD+N ≤ %, VDD = 5.0V 1.35W (typ)■ Headphone Amplifier RL = 32ΩPOUT, THD+N ≤ %, HPVDD = 1.8V 19mW (typ)LM49155主要特性：■ Noise cancellation for uplink and downlink without DSPtypeartifacts, distortions or delays■ Adapting AGC on ambient noise level & downlink signalstrength for earpiece■ Downlink adjustable noise-reducing high pass filter■ E2S Class D Amplifier with ALC■ Ground Referenced Headphone Outputs with Advanced Click PopSuppression■ Micro-power shutdownLM49155应用：■ Mobile Phones■ Portable Electronic Devices
图1。LM49155简化方框图图2。LM49155典型应用框图
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