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Board: OE Gravitech Nano Is it possible to destroy the board if there are a voltage on a Analog pin while the board is not powered? I have a application that use a analog (speed) voltage 0-4,9 from a GPS module, this worked very nice for a hour of 10, after that the voltage seems to be not constant available. Maybe the user have powered off the Arduino while driving the machine.

Regards, Rien

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Assuming you're talking about the device with this schematic (or similar), the "analog" pins go directly to Atmel AVR I/O pins with no series resistance, so yes, it's quite possible to damage the microcontroller. Add some series resistance of a few K and you'll have a better chance of the part surviving such an event.

The voltage on any pin should not, under any circumstances exceed Vcc+ 0.5V as the datasheet specifies, however it's usually okay under non-operational conditions if the current is limited to much less than the 40mA. A 4.7K resistor would limit the current to less than 1mA with a 5V input.

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  • So if I understand this correct, if VCC are 0 (Arduino not powerd)a signal higher then 0.5V on a Analog input pin destroy the Arduino? – Rien Brand Apr 23 '15 at 6:39
  • Sort of. I'm going to a be a bit persnickety about this. It says that if you keep the voltage less than 0.5V with Vcc = 0 you will not destroy the Arduino immediately. In fact you can exceed that voltage if the current is limited (series resistor) without immediately destroying the chip (the voltage might go up to 0.7V or 1V with a few mA flowing). Nothing is said about proper operation under these type of circumstances. The data sheet does not say this explicitly, but if you put several volts on the input with Vcc held to 0V, you will destroy the chip. – Spehro Pefhany Apr 23 '15 at 15:01

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