Can we really have a four-day battery in a PDA?

by Guy Kewney | posted on 21 January 2003

A project has been set up between chip designer, ARM, and silicon power supply provider National Semiconductor. The object is to increase, by a factor of four, the battery life of hand-held portable devices.

Guy Kewney

The ARM risc processor has long been the absolute leader in processing power with "low gas mileage" as Americans car adverts put it; it uses relatively little energy when running. But the problem of keeping power consumption down isn't just a question of fitting a low-power component into the electronics: there has to be some co-operation between battery and computer.

So the two companies have announced a strategic business relationship "to develop and market power efficient systems that will increase the battery life of handheld portable devices - in several stages - from 25 percent up to 400 percent."

The key will be "an advanced technology that enables ARM Powered system-on-chip (SoC) devices to dynamically adjust performance and power consumption to maximise energy conservation in portable devices," said the companies, announcing the deal.

Proof-of-concept demonstrations of National's PowerWise technology and ARM's Intelligent Energy Manager technology went on display at National's booth at Electronica 2002 last November 12-15, in Munich.

The important factor which has to be born in mind is that nobody expects battery technology to be able to deliver the magic. The only way of doubling the power of a battery, is to double its weight.

That's no longer acceptable in pocket devices. So it has to be done by clever use of the power that is available. Phones have been working on this to the point where they can keep a charge for days; by comparison, PDAs are looking disastrously expensive to run in power terms.

"Consumers are demanding better performance and longer battery life from handheld devices," said Peter Henry, vice president for portable power products at National. "Every time you add a new capability such as multimedia systems or digital photography, it takes more power and reduces the lifetime of your battery. The only way to give consumers what they want --- more features and longer battery life --- is to improve the management of power consumption in portable devices. That is what National and ARM want to accomplish."

In current practice, processor vendors and power management IC manufacturers develop their technologies separately. Despite many improvements, power efficiencies are reaching levels where only minimal gains can be achieved through conventional approaches.

"National and ARM intend to change this paradigm by developing a holistic system-level approach that intelligently manages performance and power consumption within an embedded system," said the joint announcement.

The first phase of products will increase the efficiency of the digital baseband by 25 to 75 percent. This collaboration, benefiting handset manufacturers and consumers, is the first of its kind to address system-level power management for an expanding and demanding portable market.

This programme hopes to exploit the dominant position of ARM and National in their various markets. ARM's penetration into the mobile phone market is guessed to be more than 70 percent and National Semiconductor's expertise in analog and power management is, if not equally dominant, certainly not second to anybody obvious. The overall handset market, including mobile phones, smartphones and handheld devices, is expected to grow to more than 525 million devices by 2006, an increase of 31 percent from 2002, according to research firm In-Stat/MDR. But the growth in PDAs is handicapped by size and weight problems.

"Innovative energy conservation for mobile and handheld applications is essential for the development and proliferation of advanced multi-media capable devices," said Mike Muller, chief technology officer of ARM. He hopes to combine two advanced technologies: PowerWise technology from National, and ARM's Intelligent Energy Manager technology.

PowerWise technology is an umbrella solution that will be developed in several phases, with the first phase targeting embedded SoC devices in mobile phones.

"The heart of the solution is a synthesizable AMBA methodology–compliant macrocell that works together with ARM Powered processors. It communicates with external PowerWise compliant power management chips using a PowerWise interface to reduce the system power supply to the absolute minimum necessary to meet the required level of performance."

ARM's Intelligent Energy Manager solution implements advanced algorithms to optimally balance processor workload and energy consumption, while maximizing system responsiveness to meet end-user performance expectations. The Intelligent Energy Manager technology works with the operating system and applications running on the mobile phone to dynamically adjust the required CPU performance level through a standard programmer's model. The PowerWise on-chip macrocell then adaptively sets the minimum required power supply delivered by the external compliant power management chip.

National and ARM are working jointly with lead Partners and third parties to standardize the software programmer's model and the PowerWise high-speed, low-power interface between the SoC device and the external power management chip. Long sought by the market, these kinds of open standards will ensure supply-chain flexibility for manufacturers of personal electronic devices.

National and ARM are also collaborating with other Partners to develop compatible OS support, design tools, and other necessary technologies. The joint solution will sample to key customers in the second quarter of 2003. Customers will be able to license the PowerWise synthesizable core directly from ARM and the external power supply chips from National.

For additional information, visit powerwise.national.com or www.arm.com/powerwise.