BUT, there is no I/O supply if the I/O supply is not turned on. The I/O supply has to be there.
Look, go ahead and ignore me if you like. But I talk to the designers of this device daily and support hundreds of customers daily. And I see boards come into the RMA department all the time with blown processors due to this issue. The power sequencing diagram is there for a reason due to the multiple voltage rails inside this device. Violate the power sequencing and you will have issues. Gerald On Mon, Feb 24, 2014 at 3:28 PM, <[email protected]> wrote: > [email protected] wrote: > > Gerald Coley <[email protected]> wrote: > > > [-- text/plain, encoding quoted-printable, charset: ISO-8859-1, 56 > lines --] > > > > > > Not really. The idea of powering a chip via an I/O pin will > > > always cause damage. It means voltage as specified by the datasheet of > > > the component. > > > > > I don't aim to 'power' it via the I/O pin! Maybe that's your way of > > saying it but it's a very odd way. The likelihood is that there will > > be a biggish resistor in series with the input to limit current and > > there will probably also be some clamping diodes or maybe a buffer > > amplifier but whatever you do there *cannot* be 'no voltage'. > > > > What I'm asking really is what will be tolerated with no problems, > > every chip spec I have ever seen specifies some sort of minimum, not > > zero. > > > ... and the processor spec *does* tell me! > > The limits are specifically stated (as I expected) as follows:- > > "Steady state max. voltage at all I/O pins" > "-0.5 volts to IO supply voltage +0.3 volts" > > So, even with power off, some voltage *is* allowed and in fact it > should be fairly easy to keep the voltage within these limits using > Schottky diodes for clamping. > > *This* is what I've been asking for. > > -- > Chris Green > ยท > > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/groups/opt_out. > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
