NXP 公司的TFA9881是 3.4W 脈沖密度調制(PDM)輸入D類(lèi)音頻放大器,它的輸入接口是過(guò)取樣的脈沖密度調制(PDM)碼流,通過(guò)該接口接收音頻和控制設定如靜音,增益,脈寬調制(PWM)輸出斜率,剪輯控制和擴展帶寬.工作電壓2.5V-5.5V,對于4歐姆/20uH的負載效率高達90%,輸出噪音電壓24uV,信噪比為103dB,主要用在手機,PDA,手提游戲機,PND,筆記本電腦/上網(wǎng)本以及MP3播放器/PMP等.本文介紹了TFA9881主要特性和優(yōu)勢,方框圖和典型的立體聲應用電路.
TFA9881: 3.4 W PDM input class-D audio amplifier
The TFA9881 is a mono, filter-free class-D audio amplifier in a 9-bump WLCSP (Wafer
Level Chip-Size Package) with a 400um pitch.
The digital input interface is an over-sampled Pulse Density Modulated (PDM) bit stream.
The TFA9881 receives audio and control settings via this interface. Dedicated silence patterns are used to configure the control settings of the device, such as mute, gain, Pulse Width Modulated (PWM) output slope, clip control and bandwidth extension (this control mechanism is not required if the default settings are used). The Power-down to Operating mode transition is triggered when a clock signal is detected.
The device features low RF susceptibility because it has a digital input interface that is insensitive to clock jitter. The second order closed loop architecture used in the TFA9881 provides excellent audio performance and high supply voltage ripple rejection.

TFA9881主要特性和優(yōu)勢:
Small outline WLCSP9 package: 1.3x 1.3x 0.6 mm
Wide supply voltage range (fully operational from 2.5 V to 5.5 V)
High efficiency (90 %, 4ohm/20 uH load) and low power dissipation
Quiescent power:
6.5 mW (VDDD = 1.8 V, VDDP = 3.6 V, 4ohm/20 uH load, fclk = 2.048 MHz)
7.8 mW (VDDD = 1.8 V, VDDP = 3.6 V, 4ohm/20 uH load, fclk = 6.144 MHz)
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應用:
Mobile phones
PDAs
Portable gaming devices
Portable Navigation Devices (PND)
Notebooks/Netbooks
MP3 players/Portable media players