[sdiy] SSM2164 protection

[David G. Dixon]

> A possible solution...
> 
> http://www.richieburnett.co.uk/temp/protect.GIF

That looks like a nice solution, but that zener is going to be a current
pig.  You wouldn't want one of those on every module with a 2164 on it!
Perhaps this could be a system-wide solution (and in that case, perhaps the
logic-based solution with the power MOSFET is better...?).