Extreme Processing Thresholds: Low Power #1

Friday, April 2nd, 2010 by Robert Cravotta

[Editor's Note: This was originally posted on the Embedded Master

In the previous Extreme Processing post about low cost processing options, I touched on what techniques processor vendors are using to drive down the price of their value line devices. However, the focus of these companies is not just on low price, but on delivering the best parts to match the performance, power, and price demands across the entire processing spectrum. Semir Haddad, Marketing Manager of the 32-bit ARM microcontrollers at STMicroelectronics, shares “Our goal ultimately is to have one [processor part] for each use case in the embedded world, from the lowest-cost to the highest-end.”

In addition to extreme low cost parts, there is increasing demand for processors that support longer battery life. Similar to low cost processor announcements, there is a bit of marketing specmanship when releasing a device that drives down the leading edge of the lowest energy usage by a microcontroller. The ARM Cortex-M3 based EFM32 Gecko microcontrollers from EnergyMicro claims a 180 μA/MHz active mode power consumption. Texas Instruments’ 16-bit ultra-low power line of MSP430 microcontrollers claims a 165 μA/MIPs active mode power consumption. Microchip’s new 8-bit PIC1xF182x microcontrollers claim a less than 50 μA/MHz active current consumption.

There are many ways to explore and compare low power measurements, and there have been a number of exchanges between the companies including white papers and YouTube videos. We can explore some of these claims over the next few posts and discussions, but for this post, I would like to focus on whether the use of μA/MHz benchmark is appropriate or if there is a better way for low power processor vendors to communicate their power consumption to you. In the case of the Texas Instruments part, 1 MHz = 1 MIPS when there is no CPU clock divider.

If the μA/MHz benchmark for active operation is appropriate for you, is there any additional information you need disclosed with the benchmark so that you can make an educated judgment and comparison between similar and competing parts? The goal here is to help suppliers communicate the information you to more quickly make decisions. I have a list of characteristics I think you might need along with the benchmark value, and I will share it with you in the next post after you have a chance to discuss it here.

If the μA/MHz benchmark is not appropriate for you, what would be a better way to communicate a device’s relevant power consumption scenarios? I suspect the μA/MHz benchmark is popular in the same way that MIPS benchmarks are popular – because they are a single, simple number that is easy to measure and compare. The goal here is to highlight how to get the information you most need more quickly, easily, and consistently. I have some charts and tables to share with you in the follow-on post.


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