AVR-Chat

--- In AVR-Chat@yahoogroups.com, "Steve Hodge" <steve@...> wrote:
>
> ... Phillips App Note AN97055 ...

Yes, I think this is the canonical reference for this type of level translator.  The description of the operation again states that the MOSFET will turn on when the source is pulled below the gate by the threshold voltage, even though what is pulling it low is a diode from the drain, which is therefore at a lower voltage than the source.  I cannot agree with this analysis, but I could be wrong.  The MOSFETs recommended are, of course, all NXP products, and I would prefer to have a wider choice.  As far as I can tell, they have been chosen based on their gate-to-source threshold voltage (other parameters are easy to meet), which just increases my puzzlement.

Anyway, I think this subject isn't as interesting to others in the group as I thought it might be, so maybe we've reached the end of discussion.  I thought someone with an analog background might point out the error in my thinking.  Note that I'm not actually facing this problem right now; it's just an intellectual exercise.  I may have some work coming in soon, interestingly enough with a large analog content, so I may then be less inclined to stir up trouble.

Graham.