VCCIO Voltage Change

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Furthermore, a similar specification of a Vih,max value can't be found with any other logic device, I think. Personally, I won't take the specification too seriously, but don't suggest to ignore it, of course.

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I checked the Cyclone III, Cyclone IV and Stratix IV specifications, which I all used recently, and they all define Vih,max. They also define an overshoot voltage of 3.95 or 4V, for 100% of the time. I'm willing not to take these specification too seriously, but I also don't want to take too much risk, so I still wonder if someone knows the answers to the previously asked questions:

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So in the most worst-case situation at VCCIO of 1.2V, can I set my input to 3.95V for 100% of the time without damaging my component?

May I pull-up the opendrain CONF_DONE to 3.95V if VCCIO is 1.2V?

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Thanks, Ton

I would ask support, if they can tell what exactly happens in this situation and if there's a risk of either device damage or temporary functional failure. I fear, you don't get a satisfying answer.

At days of MultiVolt I/O Interface specification, there has been a comment about possible increased leakage currents when overdriving inputs. As one explanation, leakage currents may have increased above reasonable bounds with newer chip technologies.

The other point is, that since Cyclone III publications are accompanied by permanent "watch your step" directions related to 3.3V operation, as if the authors can't imagine that a designer would be ever able to manage overshoots and keep the maximum voltage ratings. Forbidding input overdrive may be another means to save the chip in this view.

Frank

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I would ask support, if they can tell what exactly happens in this situation and if there's a risk of either device damage or temporary functional failure. I fear, you don't get a satisfying answer.

Frank

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I filed a service request and the answer was only partly satisfying.

There is a kind of multivoltage I/O application note for Cyclone III and IV.

It is AN447 (http://www.altera.com/literature/an/an447.pdf) (http://www.altera.com/literature/an/an447.pdf%29). This application note however is limited to 2.5V, 3.0V and 3.3V I/O.

Although I try to push him a bit, the application engineer advices to keep the input voltage below te recommended Vih,max.

An overshoot voltage of 3.95V can be applied for 100% of the time over a 10 year period.

I don't get any statement about what happens when I drive the input with a voltage between Vih,max and Vovershoot.

Regards, Ton