user8638: 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

user5080: 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. 


8638: <p>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.</p>

<p>Regards,
Rien</p>
 5080: <p>Assuming you're talking about the device with <a href="http://www.mouser.com/pdfdocs/ArduinoNano30_schematic.pdf" rel="nofollow noreferrer">this schematic</a> (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. </p>

<p>The voltage on any pin should not, under any circumstances exceed Vcc+ 0.5V as the <a href="http://www.atmel.com/images/Atmel-8271-8-bit-AVR-Microcontroller-ATmega48A-48PA-88A-88PA-168A-168PA-328-328P_datasheet_Complete.pdf" rel="nofollow noreferrer">datasheet</a> 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. </p>

<p><img src="https://i.stack.imgur.com/lBahq.png" alt="enter image description here"></p>
