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Topic: Can arduino adc take negative voltage or not? (Read 528 times) previous topic - next topic

yaantey

The datasheet mention 0 to 5V. So does that mean the ADC cannot take negative voltage. And that the max amplitude of the analog wave should be 5V and min amplitude should be 0V?

Thanks

Graynomad

#1
Jan 31, 2012, 02:32 pm Last Edit: Jan 31, 2012, 10:51 pm by Graynomad Reason: 1
That's about the size of it. You can go just a little under/over but only about .5v IIRC.

______
Rob
Rob Gray aka the GRAYnomad www.robgray.com

MarkT

No it can't.  The chip is a standard CMOS process, if you go more than about 0.5 beyond the supplies you can cause latch-up(*), burn out the protection diodes, generally bad things happen.

If you want to protect the inputs one method is to add schottky diodes to the supply rails to prevent the line going more than about 0.4V out of range (effectively you bypass the on-chip protection diodes completely).

(*) latch up is a CMOS-only failure mode where the chip sudden starts conducting large currents and overheats.  Too much current through the internal protection diodes can trigger this I think.  Only cure is remove supply.

http://en.wikipedia.org/wiki/Latchup
[ I won't respond to messages, use the forum please ]

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