MaximMAX9879立体声D类音频功率放大方案  2012/3/1

         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 a16ohm ?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 9dBMargin Under EN 55022 Class B Limits with No Filter Components

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