[sdiy] SSM2164 last time buys

[Colin f]

> The first thing I thought of was a relay based solution, but 
> that seemed a bit overkill for one PCB. I was hoping there 
> was something simple that could be built onto a PCB with a 
> few cheap components, rather than a system wide solution.

I'm not sure the problem here is clearly defined.
Is it a lack of a negative supply when the positive and ground rails are
present ?
Is it the presence of input voltages below the level of the absent negative
rail ?

Cheers,
Colin f