[sdiy] SSM2164 protection

[Richie Burnett]

A possible solution...

http://www.richieburnett.co.uk/temp/protect.GIF

T1 is only turned on and supplies V+ to the SSM2164 when the -15V supply rail is
larger than a certain voltage.

ZD1 determines turn-on voltage, probably something around 20V.  R2 chosen to
provide sufficient base drive to support the required collector current to drive
SSM2164 devices on the switched V+ rail.  R1 to turn off T1 in absence of
sufficient V+/V- voltage difference.  T1 any PNP with sufficient current
handling, decent hfe, and Vce sufficient to comfortably hold off total supply
voltage plus any spikes etc.

May also need anti-parallel diode across T1 collector-emitter if the SSM2164
needs to return current to the V+ rail in order to operate properly?

-Richie,