(April 2004) The hierchy of energy systems should be examined closely

Motorolaís Jason Howard offers a formula for selecting the power source of a new product. He identifies four categories of importance.  They are: show-stoppers, game-changers, enablers and differentiators.  

Show-stoppers include product safety, regulatory compliance and cost.

Game-changers include power and energy density. Movement away from Nickel-cadmium and Nickel-metal hydride to Lithium-ion has been spurred by improving power density and lower price.

Enablers are reliability and operating environment.  For example, Nickel-cadmium is still most popular for police radios because of its extended low-temperature operation.

Differentiators include user perception and convenience.  Charging and charge management are important here.  Thin prismatic Lithium-ion cells and Lithium-ion polymer provide the slim form factor, a most desired marketing tool.

Portable Design, Jan 2004, pp 13-15k
 (April 2004) Lower SoC operating frequencies to cut power dissipation

As performance demands increase for all portable electronic devices, batteries are scorned because the packaging density improvements of semiconductors does not spill over to increase the power or energy density of batteries. The framework of such thinking is the major stumbling block to total system improvements. In this story, the author focuses on ways to achieve greater total performance by looking at what affects operating power. It turns out that as greater integration of electronics allows complete systems to be produced on a single chip (System on Chip = SoC), the product of capacitance, the square of the Voltage and the frequency determine chip power. New fabrication techniques do allow lower Voltages which drop the power by the square of the reduction, but the if the operating frequency can be reduced also,the net effect is a cube effect on power demand. One method for reducing the frequency is to analyze system software to determine where routines can be compacted to perform in fewer cycles. Fewer cycles results in a lower operating frequency, and the power demand drops. An example is presented in which a Dolby Digital decoder has a noise-level threshold of audibility computation reduced by a factor of 161.

Portable Design, February 2004, pp. 32-33