Help reading data sheet - Max current draw of my PIC?

Discussion in 'Embedded Systems and Microcontrollers' started by spinnaker, Sep 29, 2010.

  1. spinnaker

    Thread Starter AAC Fanatic!

    Oct 29, 2009
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    I am trying to read the datasheet for my PIC 18F14K22.

    I found the DC characteristics tables but I am confused as to what table to read and what line on the table.

    I am using the internal oscillator (FOSC = IRC) at 1MHZ.

    Can someone please give me some help on reading this table? What table do I pick (is it RC Run Supply Current)? What is the Param No column refer to?

    Will this table give me my total current draw of the PIC or is there something else I need to know?
     
  2. Markd77

    Senior Member

    Sep 7, 2009
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  3. spinnaker

    Thread Starter AAC Fanatic!

    Oct 29, 2009
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    I am using 5VDC supply.

    If I understand you correctly, that table then is only the current used by the chip while it is running and does not include current draw if I do an ADC?


    Maybe I should ask the question this why. I have a 5 VDC source but can only supply a max of 20 ma. Can I expect the chip to draw anywhere near that? I also still need to add in the LCD display (have not really picked one yet).

    If I back light the LCD then I plan to supply the backlight right off a 12 VDC battery (already have plans to auto shut down the light when not in use). But I might just go for a no back lite display to keep things simple.
     
  4. Markd77

    Senior Member

    Sep 7, 2009
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    I'll bet the PIC will draw less than 1 mA with everything enabled. If you look at a datasheet like the 12F675, it has graphs for the power of the comparitors, ADC, timers, etc and they are all tiny.
     
  5. maxpower097

    Well-Known Member

    Feb 20, 2009
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    I think each pin is capped at 40mah, basically enough to run a small LCD or a relay.
     
  6. sage.radachowsky

    Member

    May 11, 2010
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    You could also do it by observation - set up the PIC and test the current.

    If you sleep most of the time, then I am sure it will use far, far less than 1 mA.

    If you need > 20 mA for fast pulses, use a bypass cap.
     
  7. Potato Pudding

    Well-Known Member

    Jun 11, 2010
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    I would go by the Power Rating.

    I can't seem to get the data sheet for that MCU, and there are reports off them needing to revise data sheets, so if you are working off an old data sheet I would be careful.

    Check the errata.

    Now that I have said the required cautionary words it is possible that the problems are related to some reverse engineering vulnerability, and exposures of Intellectual Property - meaning code and data programming - that are hinted at. If you don't care about chip security and those liabilities are Microchips main concerns then you should have nothing to worry about.
     
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