Lpc2000

I've got experience with the LPC2132 not handling a brown-out 
condtion.  In my case, when the Vcc dropped to around 1V, and then 
back up to 3.3V, the CPU locked up, and would not recover.  External 
reset will not clear this condition.  The only way I found to do it 
was remove Vcc, then let it come back on.  If you have a system 
where DC power will routinely ramp down and up, and may not go all 
the way to 0V when it goes off, I highly suggest using something to 
monitor the INPUT to the voltage regulator, and turn the regulator 
off when its input is low.  The external WDT is probably a good idea 
also. 
John
--- In lpc2000@yahoogroups.com, "Andrew Berney" <amb@...> wrote:
>
> Cheers for the input guys.
> 
> The actual environment this board will live in is on a steel 
propeller shaft
> rotating at up to 1000Rpm (not an ideal environment but given its 
job is to
> measure physical parameters of the shaft somewhat unavoidable). 
Due to the
> nature of the rotation and required freedom, power is provided by 
induction
> from a power head mounted close to the shaft, however this can 
lead to
> intermittent problems with power loss/surge. Surge and spikes we 
can deal
> with electronically however power drop/loss can lead to the ramp 
condition
> you both describe. Hence I'm looking at the potential use of an 
external
> supervisor / WDT and wondered if anyone had had any prior 
experience using
> them with the Philips Micros.
> 
> 
> 
> -----Original Message-----
> From: lpc2000@yahoogroups.com [mailto:lpc2000@yahoogroups.com]On 
Behalf
> Of unity0724
> Sent: 11 March 2006 01:53
> To: lpc2000@yahoogroups.com
> Subject: [lpc2000] Re: Use of external reset supervisor chips
> 
> 
> Sorry, could not fully understand your question.
> I was suggesting extra external hardware WDT to Mr Andrew Berney as
> there might be cases of CPU not starting up, even with H/W
> reset/power supervisor.  His type of working condition is just too
> tough for the CPU.
> 
> If external hardware WDT is installed, this type of hardware WDT 
are
> normally cleared by reset (Power supply below threshold level) and
> will start to "WDT ticking" only after the reset (Power is above
> threshold level + some reset delay).   It will always ensure some
> fixed WDT timeout after reset before that WDT "bites" (typically 1-
2
> seconds).
> 
> For the core voltage delay, it is the duty of the reset/power
> supervisor chip to have enough extra reset delay, typical 50-200mS
> (extra reset delay after 3.3V power good to be longer than your 
1.8V
> LDO ramp delay)
> 
> Regards
> 
> --- In lpc2000@yahoogroups.com, "lpcarmed" <lpcarmed@> wrote:
> >
> > I had startup issues when the power supply did not ramp up the
> voltage
> > fast enough. The reset supervisor will make sure you reached the
> > operating voltage and then apply the delay. If your CPU is locked
> up
> > in a slow startup of the core voltage when peripheral supply
> already
> > applied the watchdog might not work. Is there a specification for
> > these conditions?
> >
> > --- In lpc2000@yahoogroups.com, "unity0724" <unity0724@> wrote:
> > >
> > > Wow, very tough working condition for that Arm Chip...
> > > and interesting...  :)
> > >
> > > May be you should use both power supervisor/monitor chip +
> external
> > > Hardware WDT. => WDT "kicks" the CPU again if it does not power
> up
> > > properly.
> > >
> > > I've seen some AVR chips flash program-able for WDT always on
> after
> > > reset.  (WDT default as on after reset)
> > >
> > > Could you help eMail me your experience after the project??
> > > Thanks in advance!
> > > Regards
> > >
> > >
> > > --- In lpc2000@yahoogroups.com, "Andrew Berney" <amb@> wrote:
> > > >
> > > > Hi all,
> > > >
> > > > We're currently in the process of putting together a device
> that
> > > will be
> > > > powered via an induction ring and as such there is the
> potential
> > > for the
> > > > device to lose sufficient power intermittantly.
> > > >
> > > > I was wondering on peoples' general opinion of using an
> external
> > > supervisor
> > > > chip to ensure a clean startup by keeping reset pulled to
> ground
> > > for a
> > > > period of around 150 milliseconds.
> > > >
> > >
> >
> 
> 
> 
> 
> 
> 
> 
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