Maxim公司的MAX98400A/MAX98400B是高性能热效率高的D类音频放大器, MAX98400A能向8欧姆负载提供2x20W或向4欧姆负载提供1x40W, MAX98400B则向8欧姆负载提供2x8W功率.单电源8V 到28V工作,提供67dB PSRR,12V时的效率高达90%,主要用在LCD/PDP TV,LCD监视器,MP3坞站和笔记本PC.本文介绍了MAX98400A/MAX98400B主要特性, MAX98400A/B功能方框图,以及MAX98400A立体声和单声道配置图, MAX98400 D类音频放大器参考设计主要特性,电路图,材料清单和PCB布局图.
The MAX98400A/MAX98400B Class D amplifiers provide high-performance, thermally efficient amplifier solutions. The MAX98400A delivers 2x20W into 8I loads or 1x40W into a 4I load. The MAX98400B delivers 2x12W into 8I loads.
An integrated limiting circuit prevents output clipping distortion, protects small speakers from transient voltages, and reduces power dissipation.
A thermal-foldback feature can be enabled to automatically reduce the output power at above a junction temperature of +120NC. Traditional thermal protection is also available in addition to robust overcurrent protection.
The ICs operate from a single 8V to 28V supply and provide a high 67dB PSRR, eliminating the need for a regulated power supply. They offer up to 90% efficiency from a 12V supply.
Filterless modulation allows the ICs to pass EN55022B EMI limits with 1m cables using only a low-cost ferrite bead and small-value capacitor on each output. Both devices feature eight digitally controlled gain settings.
Comprehensive click-and-pop reduction circuitry minimizes noise coming into and out of shutdown.
The MAX98400A/MAX98400B are available in 36-pin and 24-pin TQFN packages, respectively, and are specified over the -40NC to +85NC temperature range.

MAX98400A/MAX98400B主要特性:
Wide 8V to 28V Supply Voltage Range
Single-Supply Operation
Low EMI: Active Emissions Limiting
Clipping Limiter
Low Quiescent Current
Thermal Foldback
Thermal and Overcurrent Protection

MAX98400A/MAX98400B应用:
LCD/PDP Televisions
LCD Monitors
MP3 Docking Stations
Notebook PCs

图1.MAX98400A功能方框图

图2.MAX98400B功能方框图

图3.MAX98400A立体声配置图

图4.MAX98400A单声道配置图

MAX98400 D类音频放大器参考设计
This reference design demonstrates the use of the MAX98400 Class D audio amplifier in a stereo audio docking station application. The MAX98400 2.1 demo box is a complete powered speaker dock that uses two MAX98400 ICs to drive a 3-channel speaker system consisting of two 2in satellite speakers and one 5in subwoofer. The reference design is intended to be used with a portable audio player as its main music source. The overall solution size is very compact and features active equalization, powersupply monitoring, and dynamic equalization for the subwoofer.

图5. MAX98400 D类音频放大器参考设计外形图

MAX98400 D类音频放大器主要设计特性:
Compact all-in-one design
Operates from a single 12V to 20V DC power supply
High SPL output from a small box
High-efficiency Class-D design
Active EQ, including dynamic bass equalization
Excellent sound quality from cost-effective drivers

图6. MAX98400 D类音频放大器参考设计电路图(1)

图7. MAX98400 D类音频放大器参考设计电路图(2)

图8. MAX98400 D类音频放大器参考设计电路图(3)

图9. MAX98400 D类音频放大器参考设计电路图(4)
参考设计材料清单:




图10. MAX98400 D类音频放大器参考设计PCB布局图