[sdiy] SSM2164 protection

[David Brown]

My cabinets are 24U.  I found that my Power One supplies would 
sometimes crowbar with the capacitance loading of that many modules, 
and it was usually the -15 rail that tended to crowbar.  I do have 
some photos each rail powering up at 
http://modularsynthesis.com/modules/DJB-power/djbpower.htm.  You can 
see the -15V rail took longer to reach full voltage.  I never 
investigated why the -15 volts was so much longer than +15 volts.  I 
don't know if that is a characteristic of the power supply or the modules.

I designed a power sequence circuit to delay half the cabinet since I 
had two power distribution boards.  In retrospect, it might have been 
worth adding some logic so that both supplies would have to be valid 
before enabling both, and to use two units with different 
delays.  You could easily overcome the voltage drop by just adjusting 
the supply output to compensate.

Just a thought of combining multiple functions.  It wouldn't be a 
problem with the smaller cabinets.

Dave

At 11:42 AM 3/2/2011, David G. Dixon wrote:
>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
>[stuff deleted]
>OK, where's the flaw?