>I'm using a PIC16F628 powered by 6V lithium batteries (KL2CR5).
>When new their open circuit voltage is 6.5V.  The max Vcc in the
>specs for a 628 is 5.5V

I have no idea what your application is, but if it would fit in a 16F84, the
maximum spec for that chip is 6 V.  The "absolute maximum" rating is listed
at 7.5 V, so you might be able to push it with a 6.5V source, especially
since a battery should drain down quickly anyway.

People are generally vehemently opposed to overdriving chips, so beware.
However, I've often run chips at .5V over spec without any visible problems.
  That's not to say it's RIGHT, it's just a fact.  Most of my stuff is hobby
work, so I guess it wouldn't matter much to me if I fried a chip here or
there.  Your application may be different.  It's up to you.

>I didn't use a switching supply because I was pushed for time.  The
>device has to last 5 years on a battery and I didn't want to spend
>time calculating which would be the best solution.

From this statement, it sounds as if your application is not a critical one,
so you may be able to overdrive your chip.  If not, then why wouldn't you
spend a few hours and calculate the best power supply option?  Especially
for a product that must last 5 years.

--Andrew

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