By Pallab Chatterjee
While there have been great strides in process scaling for power reduction on a per-gate level for mobile devices, a large part of the power is still consumed by the power amplifier, filter and analog mux arrangement from the systems.

Most of the logic systems have benefited from scaling to the sub-40nm technology range, which reduces standby and operating power by several orders of magnitude compared with traditional 130nm technologies. The small size allows very complex systems using small pin size and serialized interfaces to fit into the reduced form factor of today’s modern mobile devices. But that has proved to be both a benefit and a drawback. These devices are now designed to communicate with multiple wireless interface standards. For example, a standard North American smart phone can communicate on four different cellular bands, two different WiFi bands, and additional mesh and local networks such as Zigbee and Bluetooth. The WiFi band amplifiers need to work with the 2.5GHz and 5GHz channels and support multiple protocols. As a result, at least two power amplifiers (PA) are needed to drive antennas for these two bands.

Some of the physically larger systems (tablets and laptops) can support the MIMO capability of the new 5GHz standards (802.11n and 802.11ac/ad). In this case, a separate PA and antenna are needed for each data path. A quad-band cell phone requires four separate PAs, each handling one of the bands. These are usually found along with analog muxes and filters to support the specifics of the carrier network for which the phones are assigned.

These analog blocks need to maintain high levels of signal-to-noise ratio and also support high levels of sensitivity to support the longest wireless range. This combination forces the analog blocks to run at higher voltages and use more power. The cellular and WiFi analog operate between 3.5V and 7V. Higher frequencies above the 5GHz band and up to the 60GHz band operate with voltages between 12V and 48V. The biggest issue here is not the voltage. It’s the current. In mobile devices such as tablets and phones, the current per amplifier for 2.4GHz and below is between 50ma and 100ma. The higher frequencies can draw between 200 ma and 700ma per amplifier. For this reason, the higher frequencies have limited battery-only applications and are for devices that can be plugged into the wall.

These current levels have an impact on use models, as well. For an Ultrabook with a combined CPU/GPU core chip and dual-band WiFi connectivity, the target use is for creation of graphics, video playback and gaming. For gaming in particular, the system should work fine because the data going back and forth is small after the initial scene load, so the “pulsed” use of the analog for communication should not impact the battery. However, for video viewing, the streaming data interface will be running at peak data rate for the full duration of the video, which typically lasts anywhere between 10 minutes and 2 hours.

Conservatively, the analog for a dual-band 802.11n system (5GHz)—the minimum for HD video transfer—would use 2 x 200mA + 50% additional current for other analog muxes/filters/etc. That equals 750mA for the WiFi subsystem alone. For a typical two-hour streaming movie that equates to 1500mA per hour of power. This does not take into account the power used by the display, the CPU, memory, storage, and operation of the computer on the other side of the analog Front End Module (FEM). These other components account for another 1500mA per hour of power for this same period. For a normal 15-inch Ultrabook, the systems have an 800 to 900mA per hour battery. With this scenario, the power design cannot operate in full continuous mode, and must have very aggressive and through power cycling systems.

The design use is operating at one-third the available power, so just implementing a reference design without full firmware, operating system and application software control of the power management will not provide a usable result. This scenario is typical for mobile device designers today. While the increased bandwidth requirements for data can be processed at lower power in the logic sections, getting the data there is still a major challenge area.

By Ellen Konieczny

Imagine that you go to your kitchen to get a drink and pass your home’s energy-usage monitor. Due to a recent heat wave, you see that your energy usage is already at what it usually is for the entire month. Yet you’ve still got one week left in your billing cycle. To keep the bill low, you turn your A/C thermostat up a degree and make a mental note to not keep lights on unnecessarily.

The next day, the weather is more comfortable. You log in from work and turn the A/C off completely. Such capabilities are not farfetched, thanks to plans to roll out smart-grid networks across the globe (see Figure 1). In fact, some utility companies have already tested these technologies. For such two-way communications to be realized on a grand scale, however, the infrastructure, smart meters, and millions of wireless devices involved will need to consume minimal power.

Fig. 1: The various aspects of the smart grid and how they will be connected. (Courtesy of Ember Corp.)

Emmanuel Sambuis, general manager for the metering business at Texas Instruments, says water and gas meters now require 20-year operation from the same battery. In some devices, the requirements are now as much as 25 to 30 years—particularly in areas where batteries are particularly difficult to access or where there are so many devices that changing out batteries can become expensive. In some extreme cases, companies have been developing energy-scavenging solutions that require no batteries at all.

What’s changing, however, is the addition of low-power communications technology inside of even home-area-network products, such as in-home displays and intelligent thermostats. Generally, such low-power communications are RF-based. In the case of power-line communications, regulations also apply and force the energy consumption to be minimal. To raise energy efficiency in e-metering applications, TI has developed an SoC microcontroller that integrates all metering functionality onto a single chip, with ultra-low-power operation so that only simple voltage regulation is required for a complete solution. The MCU provides direct device operation from a 3V supply with the CPU and ESP active at only 2.5 mA. During a power outage, the device can operate in standby mode at 1.1 µA with the real-time clock function active.

It is essential to keep in mind that smart-grid devices will most likely be asleep for the majority of the time. “The biggest challenge is in enabling the battery-operated devices to not be awake for long periods as well as for them to be able to join the network, acquire and process any data as quickly and efficiently as possible, and go back to sleep, said Skip Ashton, senior vice president of engineering at Ember Corp. “Designing technology–radio, processor, and networking software–which enables devices to do that reliably and securely is the crux. A user of a battery-operated device expects instant operation and control when they are using it but long battery life when they are not. This type of ‘instant-on’ capability requires coordination of the radio as well as the software controlling the devices.”

Thankfully, standards bodies like the ZigBee Alliance (www.zigbee.org) include low-power operation as a critical goal as they develop their protocols. For suppliers implementing the protocols and hardware, however, Ashton emphasizes it is important to view the technology offering as a “system” that includes hardware and software. “A tightly integrated platform, which has been developed from the ground up to work together to deliver excellent performance, efficiency in code size, and processing of security and application data, lends itself to better resolve the challenge of minimizing power consumption and extending battery life. Although the standards can prescribe a certain level of behavior, different suppliers can innovate within the standard to improve performance,” Ashton says.

In addition to running IEEE 802.15.4/ZigBee wireless, for example, the MeshConnect modules and integrated circuits (ICs) from California Eastern Laboratories promise to get good range out of a very low-powered device (Fig. 2). According to David Cohen, director of marketing, and Rich Howell, director of business development, the MeshConnect modules and ICs put out +7 dBm power out native (i.e., without using an external power amplifier). The MeshConnect technology delivers standby mode at less than 0.3 µA.

Figure 2: With sleep-mode power consumption below 1 µA, the MeshConnect Extended Range Module offers extended battery life

Although such products are impressive innovations on their own, they are only part of a bigger picture. A successful smart grid will require close collaboration between providers of communication devices (RF transceivers and processors, for example), providers of communication software, and designers of communication systems. In addition, success will largely depend on advances in signal processing.

“Smart-grid technology developers look to advanced digital and analog signal-processing technology to power next-generation energy infrastructure,” said Ronn Kliger, energy group director at Analog Devices. “By leveraging ICs optimized for a range of smart-grid applications—from energy-metering solutions to dynamic, grid-integrated management and communication systems—developers are able to design intelligent systems that promote energy efficiency and management flexibility.”

Along with energy-metering ICs, the firm offers RF, power-line carrier communication, power management, and digital signal processing in support of smart-grid applications.

Measurement capabilities also will need to be fine-tuned, as standby or “vampire” power poses a clear threat to the smart grid’s low-power-consumption efforts. Standby power results from electronic devices that are plugged into wall sockets, such as TVs, DVD players, cell phones, and answering machines. Whether they are on or off, they consume power 24 hours a day. It is difficult to accurately measure the power that they actually use, however, which is why they must be accounted for in the smart grid. A number of companies have developed ways to measure even the smallest amounts of energy usage. For example, Teridian claims to provide accuracy of +/-0.5% over a 2000:1 dynamic range.

Of course, the most frightening specter haunting power consumption in smart-grid devices may be standby current. This issue becomes especially critical for the finest silicon technology nodes, where transistor leakage current starts to dominate. Leakage power already poses a significant problem at advanced process nodes, and the problem increases with density at advanced nodes. The dynamic power dissipation arising from high-frequency switching of the tens of millions of transistors directly impacts aspects like battery life, packaging and cooling costs, form factor, and reliability.

All of the major EDA companies are now advising SoC developers to consider low power as part of the architecture rather than something implemented later in the flow, and entire flows are becoming power-aware and power optimized. That goes for the process as well as the components. Third-party IP vendors such as Virage Logic, ARM and Synopsys are now standardized on low power versions rather than splitting their product lines between IP geared for low power and performance, and even in the FPGA space, where concern for power was either an afterthought or non-issue, all of the major vendors are now offering lower-power solutions. Actel has even developed chips that rival the power consumption of some of the most advanced ASICs.

By Brian Fuller

The nation’s power grid hasn’t been upgraded in a century, but suddenly there’s a sense of urgency.

In high-profile meetings from Washington to Santa Clara in the past two months, industry executives, scientists, engineers and government officials have ratcheted up the dialogue about modernizing how energy is generated, distributed and used. The movement, helped by an expected $4.5 billion in government stimulus money, has its roots in the national concern over fossil fuel resources and heightened focus on energy efficiency.

“They’ve moved really fast throughout the month of April and May,” says Lucian Ion, strategic marketing manager for smart grid and energy technology solutions at National Semiconductor. “There’s a tremendous amount of work that’s public already from substation generation to customer’s home.”

The ideal vision, shared by many, is a truly energy-efficient system in which home appliances talk wirelessly to a device that lets consumers understand their power usage and control their consumption; in which utilities talk to homes to manage energy loads at times of peak demand, and in which utilities better manage the distribution of new, “bursty” modes of power generation such as solar and wind.

Two things make electricity unique and a challenge for smart grid: Lack of flow control and electricity storage requirements

“Change either of these and the grid delivery system will be transformed,” says Dick DeBlasio, chairman of the IEEE SCC21 Group, which oversees the P2030 Smart Grid standardization effort.

Updating a system that has worked well and consistently and remained essentially unchanged for 100 years would appear a daunting, time-consuming task, but participants are taking their cue from the Internet, another complex technology infrastructure that has grown and evolved with a focus on standards.

“The Internet was built on open standards ranging from communications and software protocols to standard microprocessors and memory,” says Adrian Tuck, CEO of Tendril, a provider of residential energy ecosystem technology and a ZigBee Alliance vice chair. “So too it can be with the smart grid.”

The focus on standardization is already yielding benefits. Shortly after a smart grid standards workshop April 28-29, Energy Secretary Steven Chu and Commerce Secretary Gary Locke hosted a Washington meeting with the National Institute of Standards and Technology (NIST) and announced 16 standards that are essentially locked down—no debate necessary.

These include:

• ANSI C12.19/MC1219-Revenue metering information model
• DNP 3-Substation and feeder device automation
• IEC 61850-Substation automation and protection
• IEEE 1686-2007-Security for intelligent electronic devices
• Open HAN-home area network device communication
• ZigBee/Home Plug Smart Energy Profile-Home area device communications.

The second big meeting Intel hosted at its Santa Clara headquarters June 3-5. Closed to the media, it was a forum for government organizations and groups such as NIST and the IEEE to begin to lay the foundations for near-term standardization work.

The goal was, among other things, to stimulate the development of a body of IEEE 2030 smart grid standards and or revise current standards applicable to smart grid body of standards.

“Our goal coming into the meeting was to get the process started and people together and in active dialogue,” says Lorie Wigle, general manager of Intel’s Eco-Technology program.

Intel’s interest is largely based in the fact that its core industry, information technology, accounts for 2% of global energy use.

“There was a really good outcome in the willingness and desire for the companies to continue to talk between meetings to make forward progress,” she adds.

At the conclusion of the meeting, three task forces were formed to tackle the next stage of standards work: Task Force 1 (Power Engineering Technology), Task Force 2 (Information Technology) and Task Force 3 (Communications Technology).

The near-term roadmap, according to NIST’s George W. Arnold, includes the initial phase between now and September in which existing consensus standards (including the 16 identified) are recognized; the establishment between now and 2010 of a public-private standards panel to provide recommendations for new and revised standards to be recognized by NIST; and testing and certification later in 2010.

While there are many existing standards and emerging technologies to work with, there are many unresolved issues.

Gaps in some of the standards—notably IEEE power engineering specs—need to be filled, according to Arnold. These include IEEE 1547 (physical and electrical interconnections between utility and distributed generation), IEEE 1588 (precision clock synchronization) and IEEE C37 (standard electrical power system device function, originally published in 1928).

The third task force’s work (communications) may be more challenging, according to Arnold, who described the communications infrastructure for the smart grid as “the Wild West.”

While most of mac/phy layer standards are IEEE’s, guidance will be needed on their application to the smart grid, and additional standards may be needed as well, Arnold says.

Within the home, ZigBee seems to have emerged as the leading wireless communications factor, although powerline and other approaches haven’t been dismissed.

The interface between the home and the utility, though, may or may not emerge as a point of contention. While it’s generally up to individual utilities to choose their communications backhaul (since they own that customer relationship), there are a number of competing ways to update the technology, according to National’s Ion. These include looking at cellular, WiMax or hybrid mesh/wired configurations—even FM radio, he adds.

“There isn’t a clear standard from how you get it from the home. That’s more of an issue of a biz model of how each utility is able to secure a backhaul spot,” Ion says.

In addition, engineers and industry leaders will be examining how to handle emerging technologies that will add load to the grid—plug-in electric vehicles, for example, that charge in a garage overnight. That requires coordination among a number of standards bodies (see chart).

Security throughout the smart grid will remain a constant as the standardization process evolves. “When it comes to running things on the Internet, things can be hacked,” Ion says. “What regulators, independent system operators and utilities are trying to make sure is that things are mission-critical.”