Low Power: Coming To A CE Device Near You

Demands from customers, consortia and regulatory agencies are forcing big changes in designs.


By Pallab Chatterjee
Low power and connectivity are the two pervasive design constraints for chips and systems being designed today, and they are showing up in devices that have not had architectural changes in decades. Some of the changes are customer-driven, some are consortia-driven, and international cooperation is making some of the regulatory-driven.

The regulatory side is moving slowly, but it is making progress. The state of California started an advanced power limit program for TVs that initially was expected to be the death of plasma TVs. However, designers have met the challenge, and along with technologies to create larger displays they have developed many new products including plasma TVs within the power limit. In fact, the plasma TV market has been staging a comeback, both in the consumer products and digital signage applications.

LCD TVs, meanwhile, have been adjusted to being dominated by LED backlighting from CFL. This has led to innovations in light-guide technology, new quantum dot technology to allow for color clarity from lower-power LED sources, and new edge film that reduce the number of LEDs needed to backlight a TV. These regulatory changes for TV have now spread to the same technology being used for computer displays without additional state or federal guidelines.

Also on the regulatory front, the set-top box (STB) and over-the-top boxes (OTT) have finally been noticed. STB devices currently do not have a power down or off state. They are on 100% of the time. The box consists of an RF-in processing section, a tuner, remote control and transcoder logic, local processing for a channel guide information to be formatted and displayed and an output RF processing section. Since a number of these blocks are not needed when the channel is not changing or the associated display device is off, power down features are coming to these boxes.

The remote control sections will go to a keep alive and search for signal structure, along with full function modes. Similarly, when a single channel is selected, then only one mode of the tuner and transcoder will be selected and set. When the TVs are off, then the RF sections are powered down. The power consumption for a typical dual-HD STB with DVR can be as high as 70W. New generation technology (power down, standby, digital tuners, etc.) utilize about 17 to 20W. SD non-DVR receivers can use upwards of 42W, while new designs are near 14W. These are now being covered by the EnergyStar guidelines.

On the committee side, the Energy Efficient Ethernet guidelines are an integral constraint on most of the new 10G, 40G, 100G and 1T standards. The PHY designs are being optimized for low latency (microsecond range) turn on from power down. These are for both electrical and optical interconnect styles. The MAC have to be able to deal with the modified packet streams, changes in block size and also support higher BER requirements on the order of 10 (-16). To handle the power constraints these systems are also handling the duality of needing new materials for smaller higher-speed backplane connections while handling longer cable interconnect lengths (up to 10Km from 2Km lengths).

The consumer side is still driven by the battery constraint based on viewing video content. Nirvana for the mobile product is to be able to display a high-definition image (something 480i or better) uninterrupted over the duration of a standard 140-minute movie or 195-minute sports broadcast. The channel has not been able to really take advantage of the improvements in battery technology, as the energy consumption from higher-resolution graphics and the power required for receiving streaming content has consumed those advances.
The first realization is close, with some tablet devices having sufficient storage capacity to hold a movie, as transferred via a powered cable, in the low-power SSD storage and do the playback without the RF being on. Some of these systems have exhibited 2.5 hours of playback capability with stereo sound.

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