[Milkymist-devel] J21: route 5V though jumper ?
werner at almesberger.net
Sat Jan 28 09:00:45 PST 2012
One more J21 issue. Having those 5V there makes me a little nervous.
Not only could any contact with them upset things I plug into J21
(which usually wouldn't be designed for 5V), but it's quite possible
that 5V could end up by mistake, be it in the design of a board
under development or just by plugging a board incorrectly, on one of
the FPGA pins. I'm not sure the clamping diodes of the FPGA would be
happy with this condition long enough for the user or developer to
notice and correct the problem.
Interesting things could also happen if the 3V3 rail gets shorted to
the 5V rail, which may be an even easier mistake to make.
To save us from this sort of troubles, perhaps we could add a
header with jumper (at some safe distance from the extension board
area) between 5V and the 5V pins of J21. That jumper would be open
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