OK, so I have a part that requires a +/-12V on it, and I do have +24V available.  So, a poor mans method would be to use a voltage divider and generate a +/- 12V and use the centertap for the ground reference.  The 'ground' or virtual ground, would be completely isolated from the rest of the circuit of course.  The kicker is that there are digital signals (SPI), referenced back to the board ground, and the part requires a digital 3.3V for this interface (actually can be 5V).  I could generate a local 5V from the +12, referenced to the virtual ground again but the only way I can see to get the SPI is to optically/transformer couple it into this section.  I believe ADI makes a part that can do this, and its not the fact that its another part, its also room on the board for another part.

Short of this idea, what other methods to generate a split supply from the +24V ?  I have very little room for much of anything, so it has to be small and pretty sure not enough room for a negative buck switcher unless very tiny.  Total current isnt going to exceed 1A


      
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