Electronic – Atmel Xmega ADC input voltage range – Can the ADC be damaged by exceeding it’s reference voltage, if the input is still less then VCC

I've been working with Atmels ATxmega parts a lot recently, and there is one question I still have that I have not been able to find a answer to, even after scouring the datasheets.

Basically, The ADC in the xmega series are somewhat limited by the fact that the \$V_{REF}\$ cannot exceed \$V_{CC}-0.6V\$. This is easily enough accommodated, I am using a 2.048V reference for the ADC with 3.3V rails.

However, I cannot determine if exceeding the ADC \$V_{REF}\$ on the ADC inputs would be actually harmful to the device.

I'm aware exceeding the \$V_{REF}\$ will saturate the ADC, this is fine in this application. However, having to clamp the input to \$V_{REF}\$ would be challenging in my application, as the \$V_{REF}\$ I'm using cannot sink any current, so if I simply used a simple schottky diode to clamp \$V_{in}\$ to \$V_{REF}\$, any excursions of \$V_{in}\$ would simply cause \$V_{REF}\$ to rise as well. I'd really prefer not to have to add a whole additional buffer just to accommodate potential occasional \$V_{in}\$ excursions.

Looking through the datasheet, I'm not really much enlightened:

The ADC IO lines are "Pin"s, so I would assume that exceeding the reference, as long as the voltage is kept < \$V_{CC}\$, while the conversion results may be invalid, it won't cause actual damage to the MCU.

On the other hand:

Note that this isn't specified as an "Absolute Maximum" value. I'm not sure if this implies that exceeding these bounds will lead to invalid conversion results, or actual damage.

I've been through both the part-specific datasheet (ATxmega32e5 in this case), and the E series databook, and neither have clarified the issue much for me.