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Maxim Integrated - Integration Nation
Len Sherman

(Dis)Integrating Power Consumption, Counterintuitively

Len Sherman
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WKetel
WKetel
6/20/2013 9:36:40 PM
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Re: Power consumption reduction.
Brad, No, actuaqlly what we need is something to run in the forground occasionally, to do the check. My issue is with those programs that do run hidden in the background.

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Brad Albing
Brad Albing
6/20/2013 1:18:43 PM
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Re: Power consumption reduction.
So, we need an app that can run in the background and see if there are any apps running in the background that aren't needed. That should help. Um, wait - maybe I just made things worse....

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WKetel
WKetel
6/20/2013 7:15:44 AM
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Power consumption reduction.
Wit all of the comments I saw no reference to any method for halting those background applications that get stuck into many portable devices, which keep running and wasting power even while not being used. Some method of reporting that an application program is still running, along with a method of stopping it from running, could result in improved battery charge life while not needing any new design improvements. Sometimes it is the invisible things that must be examined closely.

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Brad Albing
Brad Albing
5/23/2013 4:35:31 PM
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Re: Duty-cycle
OK, I understand. That's a good explanation regarding the duty cycle and overall power draw. Thanks.

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Dirceu
Dirceu
5/23/2013 12:09:35 PM
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Re: Duty-cycle
Brad,

    is not about the instantaneous current, but the reduction of average current. I explain: In the past the idea was to reduce power consumption running the processor in slower possible clock in order to execute a given task. With the emergence of low-power modes, now the concept has been slightly changed. Suppose a system uses one of the low-power modes to stay "sleeping" most of the time and only "wake up" when a task must be performed (periodically or upon external request). So, now you want to have a processor with a fast clock performing the task in the shortest time (note the success of ARM Cortex-M0 and M0+ cores). The figure below illustrates these ideas. Note that with fixed "Run" and "Sleep" currents, a lower average current will be achieved through a smaller duty cycle. Course, it was something simplified. In practice there are several distinct power levels (for example, turning an on-board radio from RX to TX mode. I discussed this in more detail in my presentation to the ESC Brazil 2011 (Introduction to Low Power RF with ARM Cortex-M0). Generally the processor "awake" by an interrupt request , such as a timer or a voltage transition on pin. Thus, the processor will attend the task more quickly (low Iavg) if it has a low interrupt latency - the time interval between the interrupt request and the execution of the first instruction on the ISR.

  In time:  I hope the author does not care too much about this slight change from analog to digital context.

 

Average current

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Brad Albing
Brad Albing
5/23/2013 9:50:41 AM
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Re: Duty-cycle
>>But then comes the issue of reaction time from sleep modes. In general, the answer given by the manufacturers is to reduce interrupt latency.

Dirceu - this goes beyond my ken as an analog design engineer - what is interupt latency and how does that affect power draw?

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Dirceu
Dirceu
5/22/2013 4:54:11 PM
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Duty-cycle

"Today efforts to save power are more intertwined with the system and require higher levels of integration. A good example is shutting off system blocks that are not used, sometimes only for a few milliseconds. This often brings constraints on sequencing and ramp rates."

   If you observe the competition between different processor on the market, will see that consumption uW/MHz in active mode is very close. Instead, are offered multiple low-power modes that, in combination with appropriate software strategy (duty cycle management) lead to a lower average current. But then comes the issue of reaction time from sleep modes. In general, the answer given by the manufacturers is to reduce interrupt latency.

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Brad Albing
Brad Albing
5/21/2013 5:44:55 PM
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Re: new materials
Well, besides the fear of running the 250V around, you may also incur additional cost with regard to UL certification issues. Which I acknowledge is part of your NRE, hence one-time, amortized over all units produced (and previously discussed here). Slight additional cost incurred due to larger PC board to get more trace separation or to accomodate oddball routing to maintain spacing/creepage distance. But that's another blog....

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Brad Albing
Brad Albing
5/21/2013 5:18:06 PM
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Re: Efficiency - is the last 1/2% worth it?
That extra 1% or 0.5% is sometimes not especially critical - unless you're the Marketing guy trying to sell product - or the customer who's trying to pit one supplier against the other and negotiate a price advantage based on that 0.5% delta.

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Brad Albing
Brad Albing
5/21/2013 5:15:22 PM
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Re: Integrated driver and MOSFETs
Derek - I went thru some of the same issues when dealing with customers while we were trying to help them decide whether to use an integrated FET buck switcher or use a controller IC plus external FETs.

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More Blogs from Len Sherman
Analog integration started around 25 years ago with the introduction of the MAX232. The device combined existing RS232 interface circuitry with a switched capacitor power supply to generate the bipolar power supply voltages used in RS232 signaling.
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