On 2/24/14, 1:28 PM, "[email protected]" <[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. Schottky diodes aren¹t going to clamp the voltage to this range. Simply use the 3V3 output from the BBB to enable the supply to your board. Regards, John > >*This* is what I've been asking for. > >-- >Chris Green >· > >-- >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.
