drawing current by microcontroller

[Kick]

Hiii guys,
What is the max. current drawing by a microcontroller PIC16F877A ??

 

[KlausST]

Hi,

it schould be in the datasheet. Maybe on some charts.
It depends on so much parameters: clock frequency, supply voltage, used periferals, external load (resistive and dynamic), power safe modes, processor load....

Hope that helps
Klaus

 

[jpanhalt]

The answer is in the datasheet, Chapter 17. Here is a snippet of part of the first page:



Apparently, the maximum current that can drawn from the power pin (Vss) is 250 mA. However, note that the ports can also sink some current, so the maximum current out (Vss) is 300 mA.

John

 

[KlausST]

Hi,

just a comment to the datasheet-snippet.

These are absolute maximum allowed data, not the operational data.
Your ucontroller will comsume a few mA.

Hope this helps
Klaus

 

[Kick]

thanks for ur reply guys..

actually I want to decide the capacity(mAh) of coin cell battery in my project.

 

[KlausST]

Hi,

for battery powered ucontrollers i recommend to use:
* low supply voltage
* low clock frequency
* internal frequency instead of external chrystal
* power safe features ( sleep, or even better: power down with wakeup on watchdog or timer....)
* no floating inputs
* switch off all periferals.

Often this drops current consuption from 10mA to a mean value of 50uA or lower....

Read the datasheets and apllication note on power safe...

Hope this helps.
Klaus

 

[malli_1729]

calculate powers for each IC in your design.
Mostly separate operation into different modes. like full ON, sleep etc
In every mode find out the voltages and current consumption of each IC. For bugger IC's like microcontrollers or Interface IC's finfout what interfaces are active and their capacitances and power consumption of each interface both static and dynamic. It will be interesting to design battery based designs.....

 

[betwixt]

For very low power consumption I wouldn't recommend using a 16F877A at all. The newer PICs use far less internal current and offer higher performance as well.

Brian.