ADC AREF question

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Having scanned through the data sheet.., I do not find a specific comment regarding any danger in driving an ADC input above (but <= AVCC) the internal 2.5V reference when it is selected as the reference. Does anyone know if doing so will result in damage?

Thanks,
John

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I would expect inappropriate operation (and maybe damage) but have had no definitive experience.

Jim

 

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The maximum input voltage for all pins except for XTAL and RESET are VCC + 0.5V. This is to ensure that the clamping diodes do not conduct. This was taken from an ATMEGA48 datasheet.

An input voltage above your Vref or AVCC should not damage the part as long as the input voltage is below VCC + 0.5V. But, your A/D will alway convert as 0x3FF. Some series resistance will give you peace of mind. But too much will affect conversion results.