Portables Spawn Various Power Techniques

Power management continues to grow in importance as portable-device sales continue to soar. That's prompting an increased focus on techniques that maximize efficiency and minimize space requirements.

The power market is booming, with growth expected to soar from $4.3 billion this year to $7.3 billion in 2008, according to Communication Industry Researchers (CIR) of Charlottesville, VA (http://rbi.ims.ca/3846-521). That's driven by shipments of many consumer devices that have huge volumes, such as cell phones and digital cameras.

OEMs and IC suppliers are taking many different tacks to improve battery life for products that have more functions, such as picture-taking cell phones. One way to trim phone size is to increase the size of the plug-in adapter. "The actual charging function for cell phones is beginning to move outside the phone, with the charge control IC being placed into the wall adapter," says Mark Richey, handheld power products marketing manager at Intersil Corp. in Milpitas, CA (http://rbi.ims.ca/3846-523).

That frees space, trims noise, and reduces heat generation inside the phone, he adds. It also makes it possible to use linear voltage regulators (LDOs) instead of more expensive devices that have greater efficiency. "Efficiency is not a big deal, since you're plugged into the wall," Richey says.

However, many others contend that LDOs are being supplanted in many applications. "Anyone who wants to charge fast and at high currents is using switched mode chargers, which are more efficient than LDOs," says Patrick Heyer, product marketing manager of portable power-management products at Texas Instruments of Dallas, TX (http://rbi.ims.ca/3846-525). These switching converters are being used to provide the many voltage levels used in today's portable products. Low-power ICs, memories, displays, and other technologies have voltages ranging from 1 to 22V, so power ICs must do many conversions.

With some end products, even the power levels going to the microprocessor will change fairly often. "Voltage to the processor will vary as a function of the operating condition, ranging from a normal 1.5 to 1.7V or a sleep mode of 1.1V," says Bernie Weir, system manager for analog portable power products at On Semiconductor of Phoenix, AZ (http://rbi.ims.ca/3846-526). Maximizing the benefits of these sleep modes is critical for systems that have far more features than in the past. "We want the quiescent current to be as low as possible," Weir says.

In high volume products like cell phones, there's a trend towards customization, sweeping many functions into the power management chip. "They are becoming complex parts, people are working on programmable power ICs, as well as making them sort of a garbage can where you put everything you can't put anywhere else," says Lawrence Gasman, president of CIR. While this approach works well with custom parts limited mainly to very high volume products, it isn't likely to see quick growth in fields with lower volumes. The costs and time of developing custom ICs are too high for many products, and it's difficult for chipmakers to develop standard parts that include these ancillary functions.