[sdiy] SSM2164 protection

[Jerry Gray-Eskue]

It should work fine if the problem is on that end, but consider that the
points of failure for one voltage are usually in the power harness or
connectors and often only one module. 

Still if we assume a reasonably reliable power harness this scheme will
protect you from the nightmare "blow all the 2164 chips" scenario.
     

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of David G. Dixon
Sent: Wednesday, March 02, 2011 1:42 PM
To: 'David G. Dixon'; 'Neil Johnson'
Cc: rburnett at richieburnett.co.uk; synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] SSM2164 protection

So, I decided it would be a hassle to try and retrofit negative-rail
protection to all the 2164s in my system.  Also, the idea of putting a
resistor on the +V pin gives me willies, and I don't relish the idea of
having to lay out special power connections for that chip on all my designs.

Hence, I'm thinking that the best solution (for me) is to retrofit the power
distribution boards in my cabinets with p-channel power MOSFETs on the
positive rail (something beefy that won't induce significant voltage drops
-- I'm thinking something like IFR9Z34, which can supply 18A).  I'll wire
the gate to the negative rail through a 20V zener (1N5357B -- thanks for the
hot tip, Richie!), and to the positive rail across a 100k resistor.
Response times should be reasonably fast, and the MOSFET will deactivate the
positive rail whether the negative rail is disconnected or grounded.

Negative rail fails, MOSFET shuts off, entire cabinet powers down safely in
less than a millisecond, 2164s spared, Dixon happy.

OK, where's the flaw?

_______________________________________________
Synth-diy mailing list
Synth-diy at dropmix.xs4all.nl
http://dropmix.xs4all.nl/mailman/listinfo/synth-diy