Maxim MAX9879立体声D类音频功率放大方案

Maxim 公司的MAX9879是高效率立体声D类音频功率放大器,并集成了立体声无电容DirectDrive耳机放大器,以D类的效率提供AB类的性能. MAX9879能从3.7V电源向8欧姆负载提供高达715mW的功率,效率88%.D类放大器在1kHz时的THD+N低于0.04%,耳机放大器的THD+N低于0.018%,主要应用在手机和手提媒体播放器.本文介绍了MAX9879的主要特性,简化方框图, 立体声模式和单声道模式的信号通路以及典型应用电路.此外还介绍了MAX9879评估板的主要特性,详细电路图和所用元件列表.

The MAX9879 combines a high-efficiency stereo Class D audio power amplifier with a stereo capacitor-less DirectDrive® headphone amplifier. Maxim’s filterless class D amplifiers with active emissions limiting technology provide Class AB performance with Class D efficiency.

The Class D power amplifier delivers up to 715mW from a 3.7V supply into an 8ohm load with 88% efficiency to extend battery life. The filterless modulation scheme combined with active emission limiting circuitry and spread-spectrum modulation greatly reduces EMI while eliminating the need for output filtering used in traditional Class D devices.

The headphone amplifier delivers up to 58mW from a 3.7V supply into a 16ohm load. Maxim’s patented DirectDrive architecture produces a ground-referenced output from a single supply, eliminating the need for large DC-blocking capacitors, saving cost, space and component height.

The device utilizes a user-defined input architecture, three preamplifier gain settings, an input mixer, volume control, comprehensive click-and-pop suppression, and I2C control. A bypass mode feature disables the integrated Class D amplifier and utilizes an internal DPST switch to allow an external amplifier to drive the speaker that is connected at the outputs of the MAX9879.

The MAX9879 is available in a thermally efficient, space-saving 30-bump UCSP™ package.

MAX9879主要特性:

♦ Better than 9dB Margin Under EN 55022 Class B Limits with No Filter Components

♦ Low RF Susceptibility Design Rejects TDMA Noise from GSM Radios

♦ Input Mixer with User Defined Input Mode

♦ Stereo 715mW Speaker Output (RL = 8ohm, VDD = 3.7V)

♦ Stereo 58mW Headphone Output (16ohm, VDD = 3.7V)

♦ Low 0.04% THD+N at 1kHz (Class D Power Amplifier)

♦ Low 0.018% THD+N at 1kHz (Headphone Amplifier)

♦ 88% Efficiency (RL = 8ohm , POUT = 750mW)

♦ 1.6ohm Analog Switch for Speaker Amplifier Bypass

♦ High Speaker Amplifier PSRR (72dB at 217Hz)

♦ High Headphone Amplifier PSRR (84dB at 217Hz)

♦ I2C Control

♦ Hardware and Software Shutdown Mode

♦ Ultra-Low Click and Pop

♦ Robust Design with Current and Thermal Protection

♦ Available in Space-Saving Package 5x6 UCSP (2.5mm x 3mm)

MAX9879应用:

Cell Phones

Portable Multimedia Players

图1.MAX9879简化方框图

图2.MAX9879立体声模式信号通路

图3.MAX9879单声道模式信号通路

图4.MAX9879单声道INB立体声INA输出`立体声模式信号通路

图5.MAX9879差分和立体声单端输入配置框图

图6.MAX9879典型应用电路

MAX9879 评估套件

The MAX9879 evaluation kit (EV kit) is an assembled and tested PCB that evaluates the MAX9879. The MAX9879 is a stereo Class D audio subsystem with DirectDrive® headphone amplifiers communicating over a 2-wire I2C interface. The MAX9879 features
user-defined input configuration, input gain, input source, output enable, and volume control. The microcontroller included on the EV kit, connected to the PC through the universal serial bus (USB) port, acts as the I2C master.

The MAX9879 EV kit also includes Windows® 2000/XPand Windows Vista®-compatible software that provides a simple user interface for exercising the features of the MAX9879. The program is menu driven and offers a graphical user interface (GUI) complete with control buttons. The EV kit comes with the MAX9879ERV+ installed.

MAX9879 评估套件主要特性:

_ 2.7V to 5.5V Single Supply

_ Proven Audio PCB Layout

_ On-Board Microcontroller to Generate I2C Commands

_ USB-PC Connection (Cable Included)

_ PCB Pads for User-Supplied I2C-Compatible Signals

_ PCB Pads for Audio Input and Output Signals

_ Windows 2000/XP- and Windows Vista (32-Bit)-Compatible Software

_ Easy-to-Use, Menu-Driven Software

_ Lead(Pb)-Free and RoHS Compliant

_ Fully Assembled and Tested


图7.MAX9879 EV套件电路图(1)

图8.MAX9879 EV套件电路图(2)

MAX9879 EV套件元件列表: