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

 

First you need to provide what cpu you´re talking about.

 

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

 

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

 

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.

 

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.

 

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