Lpc2000

--- In lpc2000@yahoogroups.com, "Etienne Lubenec" <e.lubenec@g...> wrote:
> Hello John,
> 
> My 2 cents:
> 
> > Now my question, should the MCU boot up when you power up 
> > from negative VCC as little 
> > as -0.5V? 
> 
> Can this cause a different power-up sequence for the 3.3V and 1.8V
> supplies (I guess the "-0.5V" is nominally 3.3V) ? Meaning:
> - in the "normal" case, 3.3V rises before 1.8V,
> - in the "abnormal" case, 3.3V lags a bit, and 1.8V appears first.
> You will probably need to have acces to digital scope to check that.
> 
> Sorry if you have already checked, or if this is clearly part of the
> data sheet, our project has not started yet, and I only have general
> ideas  at this moment.
> 
> 
> > Should a reset chip (I'm using TPS3836 3.3) help? 
> > In my case, it doesn't. Thanks.
> 
> Just a thought here: I feel using a 3.3V reset device on a nominal 3.3V
> supply is too tight. If on the board you use, "3.3V" is really 3.30V
> nominal, of course. I would expect problems with glitches, aging &
> temperature drifts. Unless your application warrants otherwise, I would
> recommend a 3.0V reset device.
> 
> Hope this helps
> 
> Etienne

Thanks for the ideas. One thing I forgot to mention is, if I power up with the serial cable 
unplugged, the MCU boots up properly.

-John G-