How to determine typical current for a cpu

Discussion in 'General Electronics Chat' started by nepdeep, Dec 29, 2012.

  1. nepdeep

    Thread Starter Member

    Sep 14, 2011
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    Hi, We know the typical , max and min values of voltage for the CPU. but the current in the cpu is changing ....is not it....? as far as i think it depends on how many input/ output pins are acitve.....but i have heard lot of time people talking aboiut the current ratings too....please provide me some tips or links :)
     
  2. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    First you need to provide what cpu you´re talking about.
     
  3. nepdeep

    Thread Starter Member

    Sep 14, 2011
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    I was talking in general....let us suppose the cup i am using is ATTINY2313..they say the 6[mA] or2[mA] max....now how do i determine the typical current during the operation....yuck!!...huh!!etc...but again my quesion is general....I want general answer please....


    the qestion rose when i was thinking about designing power supply...should i cosider the maximum current limit of the cpu as the worst case situation or the maximum limitation of the powersupply
     
  4. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    I am not an AVR user, but in general, you can say, the higher the speed, the higher the power consumption.
    Looking at the datasheet the Attiny has a large power supply range.
    Also the power consuption will be higher at higher supply voltages.

    The documentation page has a lot of PDF's on the Attiny:
    http://www.atmel.com/devices/ATTINY2313.aspx?tab=documents

    Bertus
     
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  5. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    There will surely be a graph in the main datasheet that shows current vs frequency and supply voltage. With larger cpus like the xmegas the consumption varies also depending on pullups/pulldowns on i/o pins and what all modules you have turned on and what power saving options you use.
     
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  6. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Put a big cap on Vdd (like 470uF) then use an ammeter to supply the Vdd to the cap.

    I have an old Avometer (moving needle type) that is great for showing a couple of mA,on its 10mA range.

    Digital ammeters tend to jump around a bit but an old moving needle type will show a current average quite nicely.
     
  7. #12

    Expert

    Nov 30, 2010
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    Yep. Can't live without at least one analog meter movement. Some things just jitter too much for a DVM.
     
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