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 capability.