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ADC current requirement

Discussion in 'Electronic Basics' started by nogoodinel, Feb 7, 2007.

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  1. nogoodinel

    nogoodinel Guest

    Im still working on ATmega16 which has buil-in A/D -converter. It
    seems that the converter is a drain for 10mA current ( 0 - 5 V ).
    Devise that feeds the analog voltage gives only 5mA ( 0 - 10 V ). So
    at the moment when I connect the lines, voltage drops heavily from
    about 4 V --> some mV.

    Is there a way to work it out? 10mA sound quite big to me. Is there a
    possibility that there are something totally wrong because the current
    requirement is so big?

    nogoodinel
     
  2. If you're saying that the ADC input pin is sinking 10mA of current, that's
    unlikely.
    Yes, something must be terribly wrong. You probably have the pin as a
    digital output with a 0 written to the pin, and it's driving the load low
    (or at least trying very hard to do so). An ADC input should be like any
    other input and look like a fairly high impedance.
     
  3. nogoodinel

    nogoodinel Guest

    I dont know if it is possible to make one pin to be digital 0 output
    and a/d converter at the same time. A/D conversion works and it is
    possible to monitor it at pc. Same time current goes 0.1 A inside
    ADC . My first message had error with zeros. Sorry. There goes so much
    current that some of the 0/1 outputs does their thing (like blink led)
    even if the Vcc is plugged out. If my chip wouldn work as it does, I'd
    say it is totally busted because of current.

    help
     
  4. nogoodinel

    nogoodinel Guest

    Yes, something must be terribly wrong. You probably have the pin as a
    YOU WERE TOTALLY RIGHT! I WAS TOTALLY LOST.

    When I put, on my opinion, pin to be digital out 0 it started to work
    after that. So it seems that my 0/I is I/0 for rest of the world.
    Thank you for your advise. I'd never would got it my self.

    nogoodinel
     
  5. Your welcome, I'm glad you got it. :)
     
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