NS公司的高效手提媒体播放器(PMP)扩展坞(Docking Station)设计方案采用LM3658SD-A双源USB/AC锂电池充电器, LM20124同步降压稳压器, DS90UR241/124 (SERDES), LM4674立体声D类放大器以及LM2735Y升压和SEPIC DC-DC稳压器, LM3478 低边N沟控制器以及AVP-1280数据转换器等.本文介绍了PMP扩展坞参考设计的主要特性以及完整的电路图,包括系统方框图,PMP电源管理和音频电路图, 双源AC/USB电池充电器和电源电路图, 3.3V主电源电路图, 扩展坞电源电路图, 视频接口(LCD)控制器电源电路图, 立体声D类放大器电路图, LCD显示系统方框图, DS90UR241串行化器电路图以及DS90UR124串并转换电路图和材料清单.
The High Efficiency Portable Media Player (PMP) Docking Station reference design showcases National Semiconductor’s PowerWise® power converters, battery charging circuitry, audio drivers and display interface. The reference design saves more power by initiating a power-saving mode when the PMP is unplugged from the wall power, automatically reducing the maximum brightness of the display as well as the output power of the audio drivers. See Figure 1 which shows the power management and audio segments of the reference design.
The LM3658SD-A dual source, USB/AC Li chemistry charger IC receives a wall wart or USB input and converts either input into a source voltage, using the LM20124 synchronous buck regulator, powers the docking station as well as providing the charging current to an external Lithium-Ion back-up battery pack.
The LM20124 provides the source voltage which biases both the audio and DS90UR241/124 serializer/deserializer (SERDES) segments of the video transport sections of the system. The LM4674 stereo Class D audio amplifier drives two 2W speakers. The LM2735Y Boost and SEPIC DC-DC Regulator boosts the 3.3VDC output to 5VDC, which supplies the bias voltage needed to charge the PMP device when docked in the docking station connector. Additionally, the wall wart also feeds an LM3478 Low-Side N-Channel Controller which boosts the voltage to 12VDC and provides power to the AVP-1280 video interface controller. The AVP-1280 converts the analog video output signal from the docking station into digital inputs for processing by the DS90UR241 serializer segment. Finally, the output of the DS90UR124 deserializer is taken and displayed by the Sharp LQ104S1DG21 TFT-LCD display, which is illuminated by an LED backlight with dimming
主要特性:
20W Wake-On-Load AC/DC Adapter provide source voltage to entire system.
Wall wart adapter or USB charging capability to Lithium-Ion battery backup.
Provides charging current for PMP device when docked in docking station connector.
Detachable LCD Display can be removed at least 10 meters from base.
Stereo Class D Audio Amplifier with logic selectable gain.
Low profile, high efficiency power management design.
Efficient LED Backlight Solution provides lighting to LCD Display. 
图1.手提媒体播放器(PMP) AVP-1280
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