Rob wrote:
>
> On Thu, 30 Oct 1997, Matt Bonner wrote:
> >
> > Further to past discussion on destructive testing of PICs (plugging them
> > in backwards, etc.) - my next rainy-day project is to run a '74A/JW up
> > to as high a temperature as it can stand.  This might take a while
> > (something like 1 deg steps every 24 hours above 150 deg).  My code will
> > test various parts functional blocks like the USART, timers, etc.  Any
> > suggestions as to good code for such a test?  Bear in mind that the
> > hardware must me minimal: '74A, crystal, and a couple of capacitors.
>
> I would do tests on time related items, such as USARTS (as you have said),
> I2C, pwm etc. Also, running the outputs at their rated currents on several
> pins to led's.
>
Not possible on the last point: Ohm's Law has to come into play at some
point.  At 25mA per pin that's 1/8 W - pretty hard to dissipate at 150
deg C.  Anyway, the only way you can get high temp out of a part is to
run it at pretty close to "storage temperature" currents (i.e.: zero).
High loads should be buffered with a VFET (VN10KE) or whatever.  BTW, at
what temperatures do LEDs melt? <g>
--Matt