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Analog read negative voltage inbuilt protection

I'm trying to read a -10 to +10V analog signal on my Arduino Mega (2560). I've been using a voltage divider to obtain a -5V to +5V signal (with two 10kOhm resistors), which used to work just fine. I'm wondering if this -5V signal can damage the Analog Input pins of the Mega ?

Thank you in advance for your time !

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+1 for finding that important spec buried inside an obscure application note.

Edgar Bonet
– Edgar Bonet

2016年09月22日 14:47:41 +00:00
Commented Sep 22, 2016 at 14:47
Well, it wasn't me: Max current for AVR IO protection diodes on AVRFreaks. I've seen that thread before so it wasn't so hard.

KIIV
– KIIV

2016年09月22日 14:54:08 +00:00
Commented Sep 22, 2016 at 14:54
It should be noted that the voltage divider is Thévenin equivalent to a ±5 V source with 5 kΩ output resistance. Thus the max current is (5 V − 0.7 V) ÷ 5 kΩ = 0.86 mA. This is assuming a 0.7 V drop in the diode.

Edgar Bonet
– Edgar Bonet

2016年09月22日 14:56:50 +00:00
Commented Sep 22, 2016 at 14:56
2

The pin might not be damaged, but he will never read anything on the negative side of the signal....

Roberto Lo Giacco
– Roberto Lo Giacco

2016年09月22日 17:37:14 +00:00
Commented Sep 22, 2016 at 17:37

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