What is AVCC for on the ATMEGA328?

Other Hardware 3rd Party Boards
1

Hi All

I am wondering if anyone can explain in plain english what the AVCC pin is for on the ATMEGA328?

Looking at the schematic for the Arduino I see it is connected to 5+ via a component L1 marked at 100uH. What is this component (an inductor/choke?) and what is it's purpose?

For my purposes of creating a perfboard arduino would I lose anything by simply connecting this pin to 5+?

Thanks

2

AVCC is power for the analog circuitry (Port C pins and internal A/D) in the Atmega.
L1 is an inductor intended to make cleaner analog power.
That is the old serial Arduino too. Newer ones have USB interface instead, with AVCC connected to VCC.

3

Hi Crossroads

So I can connect AVCC directly to VCC (5+) without providing the inductor for now?

I guess I can add the inductor at a later stage when I get one.

?

Cheers

4

Yes. Modern boards are shipping without the inductor. If you have a clean 5V source, you should be okay. If you are doing lots of fine analog measurements, you can add it later if your measurements look questionable (tho hard to tell really with 4.88mV resolution).

5

Magic

Your assistance here and in many of my other questions is really greatly appreciated Crossroads. :smiley:

6

Sorry for resurrecting the thread, I have connected AREF And AVCC pins to Vcc.
And have made a synth with dual pwm audio output, when MIDI INPUT is received it makes a crackle noise.

Here is the schematic:

It's very thin but it's there at the output, also is most noticeable at those 2 "green font markers with arrows" above

Could it be AREF and AVCC reason??? I tryed to RC low pass filtering them but it didn't do anything.
Thanks!

7

DO NOT CONNECT AREF TO AVCC. It connects internally by default.

Add 0.1uF caps from AVCC, VCC, and AREF to GND.
Add to your LM358 power pin also.