Designing all-digital audio systems for HDTVs

Rick Beale, VP of Marketing & Business Development, JAM Technologies, Inc.

August 23, 2006

Rick Beale, VP of Marketing & Business Development, JAM Technologies, Inc.

With the advent of digital recording and transmission, the idea of directly combining digital sources with digital processing to provide an end-to-end digital audio system seemed imminent. End-to-end digital audio would ensure that a digital audio source, whether a CD, DVD, or HDTV, is "heard the way it was meant to be heard" " and reproduced with the same high resolution as it was recorded or transmitted. In addition, it has enabled audio and video to be made available as a feature in a wide range of consumer products and not just standalone. The most obvious examples include audio players in cellular phones, video hard drives in TV set top boxes, and even audio/video playback in computers. This is only the beginning of the digital lifestyle explosion as the audio/video system integration increases and cost decreases.

Consumers have embraced the digital lifestyle with veracity. It was not long ago that TiVo and MP3 players and high definition TV were a technical novelty. Now, Digital Video Recorders (DVRs) and iPODs and flat panel TVs are a staple of cool, shaping today's pop culture. Consumers have come to value the convenience and coolness brought by the digital lifestyle even at the compromise of some historical measures of product quality like audio fidelity. Certainly consumers still value fidelity, and would prefer a product that sounds better, but lack of audio fidelity will not impede their adoption of the digital lifestyle. Technology must step up to bridge the gap.

System Architecture Digitization
The system architecture of consumer products has increasingly become digitized, driven by the exploding market demand for digital connectivity. New product categories like digital high definition TVs (Figure 1) have become possible with processor advances for digital signal processing and manipulation for complex functions like MPEG decoding and video scaling. Functions like filtering and demodulation that were once implemented using analog techniques are now implemented digitally with lower cost, better performance and lower power. Progressively, the digital footprint in system architectures (Figure 2) has expanded closer and closer to the real world edge, capturing an increasing amount of the system functional content.

Digital system-on-a-chip (SoC) integration has been the primary enabling technology for digitization of the system architecture and driver for price-performance explosion. True to Moore's Law, process geometries have decreased from 0.25um to 0.18um to 0.13um and now to sub 100nm. Process innovations for memories and mixed signal circuits and architecture advances in DSP/RISC processors have enabled more features to be integrated in less silicon at decreasing costs. New companies like Broadcom and Marvel have been built exploiting this powerful industry trend to the point where highly complex system architectures are now being realized in a single SoC.

The System Interface Chip Tornado
As significant as the impact of digital SoC integration has been on system architectures for consumer electronics, the fact remains that we fundamentally live in an analog world to which these big digital SoC's must interface. This system interface includes three primary functions, all of which utilize mixed signal and power analog technologies:

1. System support
2. Communication interface
3. Consumer interface

The System Support function is primarily the interface between external power sources and the increasingly complex system power management interface. The communication interface connects the digital SoC to data transport networks like Ethernet, WiFi, Bluetooth, USB, and cellular. The consumer interface bridges the digital world to the user, and includes functions like display drivers, microphone inputs, audio/video line in/out, and audio amplifier outputs to speakers.

While the SoC price-performance learning curve (Figure 3) has been astonishingly steep over the past 10 years, system interface functions have experienced a much more modest improvement. Until now, this has been rational since the digital SoC functions represented a majority of the system cost and opportunity for improvement. However, the situation has changed. The cost for the system interface function now represents a significantly large percentage of the IC content cost, creating a golden opportunity for focused investment and price-performance learning curve acceleration.

Today, three industry factors are converging to create a perfect storm around the system interface function similar to that experienced with the SoC. First, the market is being driven by demand for the digital lifestyle, fueled by the advances in creating, storing, distributing and processing digital content. Second, key semiconductor process technologies like High Voltage (HV) CMOS have become available for driving the requisite economies of scale by cost effectively integrating system interface functions that require power analog circuits. Third, innovative architecture technologies are emerging for integrating power analog functions like power management and audio amplification. As with the SoC integration trend, these three forces are reinforcing each other into a sustainable tornado for System Interface Chip (SIC) integration.