Keeping MP3 players small and inexpensive requires a one-chip solution like the STMP3400 audio decoder from Sigmatel. This device packs everything, except some passive components and the flash media, into a single chip. It drives an LCD display and headphones directly, includes a USB controller, reduces time-to-market, and lowers system costs.
The STMP3400's USB controller provides a mechanism to download MP3 and WMA files and new firm-ware. Its flash-memory interface supports most technologies, including CompactFlash, SmartMedia, Secure Digital Memory, MMC memory, and even IDE devices.
Inputs for a microphone, line in, and FM tuner allow playback and ADPCM recording from other sources. The amplified output from Sigmatel's 18-bit digital-to-analog converter (DAC) drives headphones directly, and the amplifier can be bypassed for external amplification. The DAC delivers a signal-to-noise ratio in excess of 95 dB.
The 50-MHz DSP is a 56004-compatible core. A 40k, 24-bit RAM and a 4k, 24-bit ROM support it. Firmware can be downloaded via the USB port. For example, future support for SDMI audio files can be a firmware download.
The on-chip dc-dc converter drives all internal and external hardware, thereby reducing system costs. The STMP3400's general-purpose I/O pins can be used for standard button controls, such as volume, bass, treble, and FM tuner.
Available now, the STMP3400 costs $14 in OEM quantities. The component cost for a typical design is about $20, not including flash memory or the LCD display. Evaluation kits and Windows USB download drivers are available.
Sigmatel Inc., 3815 South Capital of Texas Highway, Ste. 300, Austin, TX 78704; (512) 381-3700; www.sigmatel.com.