Internet Radio Players provide consumers with a way to enjoy thousands of radio stations via an internet connection. The low cost, low power consumption and small form factor of these devices provide an alternative to booting up a computer to listen to streaming radio. These devices typically integrate alarm clock functionality and include stereo IO and a LCD or touch screen display. Higher end devices support video playback and leverage online content such as album art and internet web browsing.
Power consumption, peripheral set and software are factors considered when evaluating the central applications processors. ARM 9 and ARM Cortex A-8 based processor families like Sitara provide a blend of power efficiency and peripheral integration by including a display subsystem for image resizing and blending and a 3-D graphics hardware accelerator. Devices such as the OMAP3530 integrate a DSP for video decoding and a video hardware accelerator for more complex video applications.
Varying levels of audio performance exist in this application space. For those seeking to hit a low price point a mono speaker provides a low-power, low-cost solution. The most common speaker configuration for this application is a 2.0 arrangement with left and right channel audio and an output power level around 10 watts. In high end systems, a 2.1 speaker configuration is often adopted to produce a more balanced sound shape. Audio processors such as the TAS3208 coupled with the TAS5711 I2S Input Speaker Power Amplifier include features such as speaker protection, audio filtering and multi-band equalization to produce rich audio performance up to 20W.
USB and stereo input ports provide the end user with access to personal electronic music libraries. Personal music libraries can be accessed via auxiliary devices such as portable audio players, USB external hard drives and satellite radio receivers. Another popular option used to connect users to existing media collections is to stream information from a networked storage device or PC hard drive over a home network. Integrating touch screen capability with the TSC2008 provides software engineers with the flexibility to create a dynamic, visually appealing and easy-to-use way for consumers to interface with their collections and personalize their systems.
The power needs of processors are different than those of speaker amplifiers. Processor power management units typically require a DC input voltage of 6 volts or less. Speaker amplifiers for this application typically require a 12 to 18 volt DC rail. One solution to create the two voltage rails is to generate the higher voltage speaker rail directly from the AC/DC stage and then step this voltage down to a DC level that can be input to the processor’s power management unit. Another solution is to start off with a lower DC voltage from the AC/DC supply to drive the processor’s power management unit and then boost this rail up to the 12 or 18 volts required by the speaker amplifier.