NXP 公司的TFA9881是 3.4W脉冲密度调制(PDM)输入D类音频放大器,它的输入接口是过取样的脉冲密度调制(PDM)码流,通过该接口接收音频和控制设定如静音,增益,脉宽调制(PWM)输出斜率,剪辑控制和扩展带宽.工作电压2.5V-5.5V,对于4欧姆/20uH的负载效率高达90%,输出噪音电压24uV,信噪比为103dB,主要用在手机,PDA,手提游戏机,PND,笔记本电脑/上网本以及MP3播放器/PMP等.本文介绍了TFA9881主要特性和优势,方框图和典型的立体声应用电路. TFA9881: 3.4 W PDM input class-D audio amplifier The TFA9881 is a mono, filter-free class-D audio amplifier in a9-bump WLCSP (Wafer Level Chip-Size Package) with a 400um pitch. The digital input interface is an over-sampled Pulse DensityModulated (PDM) bit stream. The TFA9881 receives audio and control settings via thisinterface. Dedicated silence patterns are used to configure thecontrol settings of the device, such as mute, gain, Pulse WidthModulated (PWM) output slope, clip control and bandwidth extension(this control mechanism is not required if the default settings areused). The Power-down to Operating mode transition is triggeredwhen a clock signal is detected. The device features low RF susceptibility because it has a digitalinput interface that is insensitive to clock jitter. The secondorder closed loop architecture used in the TFA9881 providesexcellent audio performance and high supply voltage ripplerejection. TFA9881主要特性和优势: Small outline WLCSP9 package: 1.3x 1.3x 0.6 mm Wide supply voltage range (fully operational from 2.5 V to 5.5V) High efficiency (90 %, 4ohm/20 uH load) and low powerdissipation Quiescent power: 6.5 mW (VDDD = 1.8 V, VDDP = 3.6 V, 4ohm/20 uH load, fclk = 2.048MHz) 7.8 mW (VDDD = 1.8 V, VDDP = 3.6 V, 4ohm/20 uH load, fclk = 6.144MHz) Output power: 1.4 W into 4ohm at 3.6 V supply (THD = 1 %) 2.7 W into 4ohm at 5.0 V supply (THD = 1 %) 3.4 W into 4ohm at 5.0 V supply (THD = 10 %) Output noise voltage: 24uV (A-weighted) Signal-to-noise ratio: 103 dB (VDDP = 5 V, A-weighted) Fully short-circuit proof across load and to supply lines Current limiting to avoid audio holes Thermally protected Undervoltage and overvoltage protection High-pass filter for DC blocking Invalid data protection Simple two-wire interface for audio and control settings Left/right selection Three gain settings:3 dB, 0 dB and +3 dB PWM output slope setting for EMI reduction Bandwidth extension to support low sampling frequencies Clip control for smooth clipping Mute mode ‘Pop noise’ free at all mode transitions Short power-up time: 2 ms Short power-down time: 5us 1.8 V/3.3 V tolerant digital inputs Low RF susceptibility Insensitive to input clock jitter Only two external components required TFA9881应用: Mobile phones PDAs Portable gaming devices Portable Navigation Devices (PND) Notebooks/Netbooks MP3 players/Portable media players
图1.TFA9881方框图 图2.TFA9881典型立体声应用简化电路图 文章来源于：http://www.szczkjgs.com/news_show_145664.htm