[sdiy] SSM2164 last time buys

[David G. Dixon]

> > Oscar: if I may ask, could you do the same experiment but
> > this time
> > with the +Ve rail disappearing?  Does that have the
> > same effect?  Or
> > is it _only_ the -Ve rail that needs careful monitoring?
> 
>  Yes of course. +V disappearing does not affect the chip, I measured
> current on negative supply when disconnecting positive supply and actually
> what it does is reduce the current.

If you look at Figure 23 of the datasheet, you'll see that the positive rail
is essentially a current source for the chip, and the negative rail is the
preferred current sink.  Lose the negative rail, and that current must go
somewhere it doesn't want to go, which (I presume) generates a lot of ohmic
heat and fries the chip.  Lose the positive rail and the current source is
harmlessly disconnected.  At least, that's my take on it (although IMBSC*).

*I may be smoking crack.