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Author Topic: Standalone proects  (Read 6281 times)
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Dubai, UAE
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Hi,

 Nick, Yours is the only version I see with AVCC decoupled, is it necessary or just a precaution ?

Duane B

rcarduino.blogspot.com


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The reference design has it, and I believe as a general rule you should decouple (all) the Vcc as close to the processor as you can.

http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html
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Hi,
   I am a big fan of Mikes site re decoupling, LEDs, Motors etc.

   I can't see any harm in having the cap on AVCC, but from this reference -

http://arduino.cc/en/uploads/Main/arduino-uno-schematic.pdf

I see only a single shared cap for VCC,AVCC,GND,AGND.

Duane B

rcarduino.blogspot.com
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Gijon - Spain
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Thanks guys, this post is really interesting smiley
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I see only a single shared cap for VCC,AVCC,GND,AGND.

Yes I see what you mean. On my "breadboard" version though, there were quite long wire runs to get to AVCC (links across the breadboard etc.) so I added the second one. On the PCB the cap is probably quite close to both pins.
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On the Atmel reference designs (search AVR042) they suggest LC filters on both Vcc and AVcc.  May not be nescessary, but for a less than a dollar in parts is not a bad idea.  I ended up using a 20-pin dip header that I placed the power LC filter, a reset circuit, power led, and a signal led.  For less than $10 is parts I was able to make 10 or so...  They make wiring up any AVR pretty easy.  

Also have a 14 pin headers with xtal circuits and AVcc LC filters

* Wire Wrap AVR Support Chip Documentation.pdf (485.7 KB - downloaded 23 times.)
« Last Edit: May 23, 2012, 08:35:23 pm by wanderson » Logged

New true random number library available at: http://code.google.com/p/avr-hardware-random-number-generation/

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