Lpc2000

At 06:34 AM 2/25/04 -0600, you wrote:
>Random guess.  Power supply sequencing and SCR latchup internal to the
>part.  Does the problem occur is both supplies are discharged to ground?
>
>"POSSIBLE" solution, i.e. untried guess.  Backbias a schotty diode across
>3.3v and 1.8v supplies so the 3.3v supply will never go below the 1.8v
>supply.  No guarantees, but something to try.

Worth a try although Philips does say there are no sequencing requirements 
on the supplies.  Actually given what they do say on the supplies I suspect 
that the I/O supply (3.3V) has wider tolerances than they admit to.

>----QUOTE---
>Hi everybody,
>
>We have designed few development boards for LPC2106.
>The schematics are posted at http://www.olimex.com/dev
>Now we are running lot of 250 pcs LPC-P1 boards and experience the
>following problem: if we program simple blinking led program into
>LPC2106 flash and then disconnect and re-connect power supply in
>random timely manner on 10 % of the boards sometimes LED doesn't
>start to blink i.e. program is not executing, but after several
>plug/unplugs LED start to blink.
>In both cases i.e. program run or program doesn't run oscillator is
>working with same frequency and amplitude i.e. it's not oscillator
>powerup problem.
>It's not reset problem also as even if we hold reset button while
>plug/unplug and release reset button after power supply is stabilized
>i.e. 1 second the code still may not run.
>The power supply is adjusted to be exactly 3.3V with 1% resistors on
>LM1117.

The 3.3V supply is for I/O so +/- 2% should be more than precise 
enough.    What's happening to the core supply (1.8 V)?

It would be worth putting an oscilloscope on both supplies and (provided it 
still happens) see what the supplies do in both the working and non-working 
cases.

Do you have a power supply monitor driving the reset line?


" '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