Lpc2000

At 05:09 PM 2/26/04 +0000, you wrote:
> >Random guess. Power supply sequencing and SCR latchup internal to the
>part.
>
>Bill,
>
>this is the exact source of the problem!
>adding 47uF capacitor to the +3.3V LM1117 removed the problem, it
>seems that for whatsoever reason on these boards +3.3V rises faster
>than +1.8V and this latch up LPC2106.
>On all our future boards we'll put 10uF to +1.8V and 47uF to +3.3V
>regulator thus will ensure some delay on +3.3V.
>
>this explains why these boards started to work when +3.3V vreg was
>working to +2.5V with insufficient Vin - in this case the output of
>+3.3V vreg rises slower and ensure the correct sequencing.

It may not be that simple.  The fact that Philips has been claiming there 
are no sequencing requirements was bothering me so I just did a simple 
experiment.  I disconnected the 1.8V supply from the micro and powered it 
up.  After the other supplies had stabilized I reconnected the 1.8V supply 
by hand.  The micro started w/o a problem.  I've got to refine the setup a 
little more but straightforward sequencing is not at fault.


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