e.Digital Corporation (fka EDIG)

[cksla]

Memory systems define consumer options for portable audio players
By EE Times
Jun 24, 2002 (7:40 AM)
URL: http://www.eetimes.com/story/OEG20020621S0073
Jon Maken,Senior Manager, Product MarketingCirrus Logic, Austin, Texas

Although experimentation will continue with portable Internet audio players, three device classes will dominate the market for the next few years: portables based on flash memory, optical spinning media, and hard disk drives. Recent flash memory price drops from more than two dollars to less than 55 cents per megabyte continue to spur growth for flash-based players. Expect this market to segment into low-end and high-end devices ranging from less than $70 to approximately $299 as consumers with active lifestyles demand a variety of innovative and ultra-portable form factors.

Optical spinning media-based portables will emerge as the dominant force. Consumers demanding the most cost-effective systems will make this class the high volume segment over the next few years due to low costs of CD-R/RW discs, consumer familiarity with the CD media, and low player costs in the range of $49 - $129.

Hard drive-based portables or jukeboxes using either 1.8-inch or 2.5-inch hard drives will deliver a fundamental advantage over all other portable devices - massive amounts of storage capacity enabling consumers to store an entire music collection on a small, convenient form factor. Consumers demanding transportability and easy access to their entire music collections will continue to drive growth in this segment.

Today's portable Internet audio customers want functional, easy-to-use devices that have long battery life and are perceived as affordable. For systems designers, this means delivering sufficient performance to playback the mainstream digital audio formats; quick system power-up with minimal delays in skipping between tracks; intuitive and easy-to-use interfaces; and a balance between performance and battery life.

As if these challenges weren't enough, navigating the digital content protection waters requires right-sizing the security capabilities to deliver cost-effective, future-proof designs. Unresolved technical and business issues as well as existing and proposed legislation continue to make this a work-in-progress.

Designers should provide a baseline security implementation flexible enough to work with Digital Rights Management (DRM) solutions, such as those from Intertrust or Microsoft. Designers should also look for solutions providing flexibility and scalability in hardware and software security.

For its part, Cirrus Logic developed what we call the MaverickKey, a method of creating a unique chip ID at manufacturing time by combining a 32-bit unique key and a 128-bit randomly generated key for each chip. A DRM can use this ID, which cannot be altered once set, to authorize or authenticate an individual Internet audio player.

Among market demands, system designers should provide full support for mainstream codecs (such as MP3, Windows Media Audio and Advanced Audio Coding) with enough performance to manage the system and user interface while providing a minimum of 10-12 hours of playback. Full support for ID3 tags and playlists for easily managing digital audio files is also a must. And, OEMs must deliver easy-to-use software compatible with mainstream encoding and audio management software for the PC and Mac.

A prerequisite for flash-based portables is a minimum of 32 Mbytes of onboard flash with an expansion slot to add more flash memory as prices decline. Also system processors should be housed in a package capable of enabling ultra-portable form-factors.

Optical spinning media portables need support for mainstream CD media types such as CD-DA, CD-R, CD-RW, 12 cm and 8 cm formats and the ability to scale to support newer optical media types. These systems should have anti-shock circuitry and firmware to minimize music skipping during system shocks. Processor hardware and firmware support for managing and error correcting low-quality CD media is a requirement to ensure maximum playback capabilities.

Hard drive-based portable jukeboxes need processors with the scalability to enable real-time encoding and storing during playback, high-quality onboard analog-to-digital converters for recording from any audio source, and an intuitive interface to support easy and quick searching and accessing the thousands of available songs.

One example of a scalable system chip for portable Internet audio players that attempts to balance performance and headroom with the power management capabilities is Cirrus Logic's EP7312. For decode purposes, we chose 74 MHz ARM7 in combination with a 48 Kbyte, zero wait-state internal SRAM memory for MP3, WMA or AAC decode workspace and buffering. The on-chip SRAM memory enables designers to reduce, and in most cases eliminate the need for external RAM while providing just enough scalability to allow support for code such as servo control code. A 90MHz version was designed to enable PC-less, real-time CD/MP3 encoding and storing during playback.

Ultra-low 90mW typical power at 74 MHz with less than 0.03mW standby was achieved by integrating a power management architecture that shutdown non-essential components and used internal timers and interrupts to allow both internal and external control of entry and exit into power management states. An integrated PLL adjusts processor frequency depending on operating mode, thus optimizing performance and power consumption. The PLL also eliminates the need for extra clock circuitry normally required to playback audio files across the most common sample rates.