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Electronics & Test
Low-Power Numbers Can Be Deceiving
9/9/2013

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Figure 2. The average current calculation for the operating cycle.
Figure 2. The average current calculation for the operating cycle.

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Rob Spiegel
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Greenwashing again?
Rob Spiegel   9/11/2013 9:31:18 AM
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I'm not too surprised that the low-power microcontrollers may not actually deliver much in the way of power savings. Seems that all new product introductions these days are somehow environmentally improved. While much of the touting is probably true, in other cases, it's just greenwashing.

tekochip
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Always check the specs
tekochip   9/11/2013 10:13:11 AM
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This is why I always ask for the specifications on news stories.  There will be some press release about a new widget that claims to run faster or jump higher, but when you read the actual specification it's the same old product with new marketing.
 
It's not always easy to get low power performance out of a micro even when the part is capable.  The right peripherals have to be on or off and I/O pins must be driven to the proper state.  Then you have to look at each function of your system to decide what the best clock speed should be.  If the system needs to wake up, perform a calculation and go right back to sleep, you'll probably want the highest clock speed, but if the micro has to twiddle it's thumbs because of a slow external device, you'll probably want to throttle back the clock since there's no sense in burning up the power.  Sometimes you'll want to balance tasks to happen concurrently and that can save power as well.
 
Anyway, system design for low power requires a great deal of design effort and really understanding how your system functions and how your uPC can perform those functions.  Just because the micro claims to be low power doesn't mean that it will perform that way in your design.


Nancy Golden
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Re: Always check the specs
Nancy Golden   9/13/2013 6:40:53 PM
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Thanks for elaborating, Tekochip - I agree! I especially appreciated the remark from the article:"As a designer, however, you shouldn't follow the advertised number blindly, but rather dive into the datasheet and check the note that gives the test conditions. Invariably, this is an ideal case, with limited relevance to the real world."

Hope for the best but plan for the worst...it usually takes some prototyping to really know what the numbers will be.

 

 

jmiller
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Re: Greenwashing again?
jmiller   9/30/2013 10:48:58 PM
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I find a couple points interesting. First the idea that an engineer would buy something without knowing what the actual requirements are for the device. Let's face it, we've all done that once or twice accidentally. And I agree about the greenwashing. Everything appears to be energy saving this or that. Cool it already. I drive a big SUV all by myself because it's neat. If I wanted to save energy I would, but since I don't, I won't. At least that's what a majority of American can buyers demonstrate with their purchasing power.

Rob Spiegel
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Blogger
Re: Greenwashing again?
Rob Spiegel   10/1/2013 11:11:37 AM
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Even if some of the energy-savings claims may be false or miniscule, it's good to see energy savings as a high value. This may have a cumulative effect of driving down energy consumption.

jmiller
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Platinum
Re: Greenwashing again?
jmiller   10/27/2013 8:30:26 AM
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I would like to know if all of the little ideas do have an overall affect.  I also wonder if legislatively we will allow this smaller efforts to replace other sources.  If we magically found an alternative to oil tommorrow would our government let us use it or would they poo-poo it because oil is bigger money.  We already have other sources of energy out there but it doesn't appear the government is really pushing them.

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