[quote:393b70d1b8="JC"]Connecting AVcc to V+ isn't a "maybe necessary" thing, it IS necessary.
As already stated in the data sheets sited above, it has to be close to V+, (hence not left unconnected).
If one was going to use the ADC then one would typically connect it to V+ through an LC filter.
If the ADC isn't going to be used then connect it directly to V+.
But, EVERY V+ & Ground pin pair, including AVcc and its associated Ground pin, should have a By-Pass cap for relaible chip operation.
Typically one would use 0.1 uF. These By-Pass caps should be connected as close to the micro's pins as possible.
So, even though the OP wants a small PCB, and light weight, the circuit should still contain the By-pass caps, ALL of them, including on the AVcc pin, (which is tied to V+).
If one leaves the ARef unconnected, (since you are not using the ADC), or tied to ground with another 0.1 uF cap, then you won't damage the micro if your code has an error and somehow sets the ARef to an internal reference option.
Generally, one would only tie this to an external voltage if was was specifically using a very accurate external voltage reference for ADC measurements, and carefully setting the ADC up to use it, (and sure one's code is bug free and can't run wild!).
JC[/quote:393b70d1b8]
Some excellent points there.
Yes you are exactly right it is not an option to connect a supply to AVCC, it is a MUST. My bad.
abracadabra, to save space you could solder some surface mount capacitors perhaps 0805 or 0603 size directly onto the chip or socket pins, assuming you are using a through hole device.
↧
