# Arduino DUE input voltage

Hello there, here is a bit of a silly questions.

When I look at the input voltage, i seen 7-12V recommended and 6-16V limit.

1) Does that mean that if I send 15V as an input it is more likely that I will damage the board or that it will live less longer?

2) About the lower bound, does that mean that it can't read anything lower that that?

First of all “input voltage” in this case refers to the potenually unregulated power supply that powers the chip and NOT the recommended digital or analog input voltage that might be seen at a port.

1. 15 means it “could” live less. Why? The enemy of electronics is heat. Most requie a regulated 5V and it’s done internally on the board. So P(lost)=(Vin-5)/(Current drawn) is power wasted as heat. At some point, the heat generated exceeds the melting point of silicon and (well you know the rest).

2. Is a little trickier. In order to regulate, you need a little more voltage than the voltage you want to compensate for losses. This isn’t always true, but for now make it true. The IC manufacturer specifies this “maximum drop”. A Silicon transistor in a linear regulator drops aroubd 0.6V and that voltage is temperature dependent. This drop could be temperature and/or voltage dependent.

So, they are saying (5-7) or two is a more reliable “overhead” than (5-6) or 1 V which is very close to 0.6 V.

So, with 6V DC input, you might not get 5V to the board under all conditions.

Thanks, I did not get that it was the input voltage used to power the board... I feel silly!

So, I read more carefully the page about it and it says:

Analog Inputs: pins from A0 to A11 The Due has 12 analog inputs, each of which can provide 12 bits of resolution (i.e. 4096 different values). By default, the resolution of the readings is set at 10 bits, for compatibility with other Arduino boards. It is possible to change the resolution of the ADC with analogReadResolution(). The Due’s analog inputs pins measure from ground to a maximum value of 3.3V. Applying more then 3.3V on the Due’s pins will damage the SAM3X chip. The analogReference() function is ignored on the Due.

Thus, if I want to measure a voltage from a photodetector, I have to be sure that this photodetector will never provide more that 3.3V. Is that correct?

Yep.

What I find perplexing is that the datasheet for the processor restricts the input voltage period.

Tradionally I/O is protected by inherent substrate diodes, so as long as the current is limited no damage will occur. Atnel has not made this statement with the Due. Mostly you see for digital inputs, that if a series resistor is used the input is protected. That does not seen to be true for the Due's processor. Also, you normally see inputs with a Vcc max, so if the processor is unpowered the current limit still has to be adhered too. Again, no such statemenet for the Due.

Hello.