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Topic: Is resistor needed for VREF pin when voltage is from divider? (Read 291 times) previous topic - next topic

mightnotshort

I measured it with multimeter. 

Vout = 1V (from voltage divider)

Hooking that 1V onto AREF pin and setting analogReference to EXTERNAL resulted in no voltage drop on the pin. I guess that 32kOhm resistor really doesn't exist.

larryd

"I guess that 32kOhm resistor really doesn't exist."

I'll put that information in my pocket ;).




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Jiggy-Ninja

There is no mention of "an internal 32K resistor on the AREF pin" in the 328P data sheet.
I am searched what I believe is the latest from Microchip, DS40002061B, from 2020.
Nor do I recall ever having seen a 32K resistor on any 328P or 2560 based Arduino board.

It's second from the bottom in the characteristics table. Took me 15 seconds to find.


Also note that min/max values are not specified, so this value is not controlled. Do not rely on it for any calculations, it's just meant to be a ballpark figure so you know about how much it's loading your reference voltage.

CrossRoads

Hmm, ok. I was searching for 32K, didn't think to look for just 32 and units elsewhere.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Jiggy-Ninja

Hmm, ok. I was searching for 32K, didn't think to look for just 32 and units elsewhere.
It also depends on which revision of the datasheet you're looking at. The one I have saved to my computer from years ago has a 50k typical value in the table, which just goes to show you how much they just don't care about controlling that particular value.


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