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Connecting avref and avcc in atmega8

  1. May 16, 2010 #1
    i am currently using an atmega8 to control my lcd.
    i am using ic7805 voltage regulator to provide for its vcc.

    i have shorted avcc to vcc. should i do the same for avcc as well.... or does it need some other external reference?
     
  2. jcsd
  3. May 16, 2010 #2

    MATLABdude

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    AVcc is the power supply for the Analog to Digital Converter (ADC), and AVref can be used for decoupling of the internal reference (i.e. it doesn't need to be connected to anything, unless you want to use a capacitor here to increase noise immunity while using the ADC). From the Atmega8 datasheet:

    http://www.atmel.com/dyn/resources/prod_documents/doc2486.pdf
     
  4. May 17, 2010 #3
    in ATmea8 avcc and vcc are shorted internaly, mega88 works better
    7805 as reference?
     
    Last edited: May 17, 2010
  5. May 17, 2010 #4

    MATLABdude

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    AVcc and Vcc are *not* shorted internally, according to the (short) pin description, and AVcc should be connected to a supply (Vcc or otherwise) even if the ADC is not being used (page 6):
    http://www.atmel.com/dyn/resources/prod_documents/2486S.pdf

    The 7805 is being used to supply Vcc, stepping it down from whatever >5V supply is being supplied.
     
  6. May 18, 2010 #5
    Last edited by a moderator: Apr 25, 2017
  7. May 18, 2010 #6

    MATLABdude

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    Last edited by a moderator: Apr 25, 2017
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