Lpc2000

At 02:29 PM 1/7/06 -0500, Tom Walsh wrote:
>Pieter Verstraelen wrote:
>
> >Hello all,
> >
> >a hardware related question: the LPC2210 has a dual power supply: 1.8V
> >core voltage and 3.3V for the I/O.
> >Is the power-on (and power-off) sequence of these 2 voltages critical?
> >Will a 1.8V regulator behind the 3.3V regulator do the job? The 1.8V
> >will be a little bit later during power-on.
> >

<snip>

>I use a 3.3v regulator feeding a seperate 1.8v regulator.  So, the 1.8v
>stabilizes before the 3.3v and the 3.3v dies before the 1.8v.  The 1.8v
>is feeding the ARM core and the 3.3v is for the external logic
>interface. Following logical flow of the powerup / power down sequencing
>of supplies would be that the 1.8v core would be active before and after
>the 3.3v stabilization / decay.  I would suspect, that internally
>reverse biasing the 1.8v core via the 3.3v could be a "bad thing"?  :-P

Experimentally I've powered the 2106 with large delays (on the order of a 
second or so)in both directions w/o any observable effect.  Both bring up 
the 3V3 before and after the 1V8 rail.  At one point philips_apps stated 
that there were no sequencing issues and that appears to be borne out in 
practice so far.

I wouldn't deliberating bring them up on widely different timescales in 
production but I also would spend effort sequencing them.  I would, 
however, put in a 'proper' power monitor chip on the reset line.

There doesn't appear to be any sequencing issues at all.  I've even run the 
1V8 at 5V accidentally w/o observable effect although I wouldn't want to 
use that chip as a production chip.

Robert

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