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Electronics => Electronics => Topic started by: ed1380 on April 10, 2010, 10:28:32 PM

Title: a2d on a 3v chip
Post by: ed1380 on April 10, 2010, 10:28:32 PM
The uc I'm using is the xmega64a3. http://www.atmel.com/dyn/resources/prod_documents/doc8068.pdf (http://www.atmel.com/dyn/resources/prod_documents/doc8068.pdf)
It has a max input vcc of 3.3v. So is the a2d only 0 to 3.3v? would I need a voltage devider?

Thanks

BTW: nice to be back ^_^
hope admin feels proud cause I'm on the AUV(autonomous underwater vehicle) team at my university lol
Title: Re: a2d on a 3v chip
Post by: tim_wang on April 11, 2010, 05:24:28 PM
According to page 67 of http://www.atmel.com/dyn/resources/prod_documents/doc8068.pdf (http://www.atmel.com/dyn/resources/prod_documents/doc8068.pdf), maximum AREF = Vcc - 0.6V, and from page 63, maximum Vcc = 3.6V, so the maximum ADC input would be 3V.
Title: Re: a2d on a 3v chip
Post by: Admin on April 29, 2010, 09:28:54 AM
Yea, voltage divider. Use really large resistance resistors to avoid power waste.


Quote from: ed1380 on April 10, 2010, 10:28:32 PM
BTW: nice to be back ^_^
hope admin feels proud cause I'm on the AUV(autonomous underwater vehicle) team at my university lol
Only proud if your team wins :P

(nice to see you back, been like 2 years?)
Title: Re: a2d on a 3v chip
Post by: ed1380 on April 29, 2010, 09:58:19 AM
I put voltager dividers on the avcc and a2d ports to lower it to 3v. ironically the EE major is doing structure and ME is doing electronics

I think I asked a question few months ago :) but we dont stand a chance again subs costing 10x as much as ours :( taking a breather this year since about 80% of the team graduated.

Hows asia? Must be nice having cheap components at hand. takes me 3 weeks to get anything lol
Title: Re: a2d on a 3v chip
Post by: Admin on April 29, 2010, 10:13:23 AM
Quote from: ed1380 on April 29, 2010, 09:58:19 AM
Hows asia? Must be nice having cheap components at hand. takes me 3 weeks to get anything lol
Totally off subject but . . . the Thai Baht has gotten 20% stronger to the dollar this year, so stuff is not so cheap any more. You'd think with all the grenades and shooting going on this month in Bangkok that the value would drop . . .

The only stuff thats cheap is old used parts, like 10 year old technology. Fine for screws and wires and such, but not circuits or sensors. That stuff is about 10% more expensive than the US, as its imported. A store just opened up selling the stuff from the US, so at least I can get it here now!