Lpc2000

There's that little gotcha of these parts being 5V tolerant only when 
3.3V is present on the i/o supply.

Since in most designs with 5V and 3.3V, one would likely generate the 
3.3V from the 5V supply, there will likely be a period of time when 
5V is present and 3.3V is not.

Unless one adds a bunch of hardware to prevent this, it sort of makes 
the 5V tolerant feature worthless.



--- In lpc2000@yahoogroups.com, Robert Adsett <subscriptions@a...> 
wrote:
> You shouldn't need the zener.  The max for the 5V tolerant inputs 
on the 
> 210x is 5.5V (as long as there is power to the I/O supply [3.3V]), 
abs max 
> of 6V.  That'll save a resistor and a zener.  Not that they'd be 
that 
> expensive to add.
> 
> Robert
> 
> " 'Freedom' has no meaning of itself.  There are always 
restrictions,
> be they legal, genetic, or physical.  If you don't believe me, try 
to
> chew a radio signal. "
> 
>                          Kelvin Throop, III