[sdiy] SSM2164 protection

[Oscar Salas]

Hello Richie,

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

This would be the solution that suggested Stewart before. It is a Zener, two resistors and a transistor  and I like it if it could be placed in the module supply input where in the PCB layout could exist more room. I mean how much current can provide the transistor?

I will breadboard it, but, could someone let me know which transistor and which voltage I need in the base. I don’t know a lot of transistors and I don’t want to burn more things :D


> 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,
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