TPS61170

The TPS61170 can provide the +12V to +15V @ 200mA but it cannot provide the -12V to -15V supply.  If you can run both +15V and -15V from the +12V supply, then I suggest the TPS61175 + external, discrete charge pump, similar to Figure 23 on page 20 of the TPS61170 but replacing the TPS61170 with the higher current TPS61175.   When designing the TPS61175 for this application, you can use the SwitcherPro tool to design a +30V, 400mA converter, then change the recommended feedback resistors to +15V instead of +30V and add the charge pump.  We have an application note (SLVA398) that will post to the web in the next few weeks that explains how to properly size the capacitor and diodes for the discrete charge pump.    Alternatively, you could use TPS54160 buck converter with a coupled inductor to get two outputs as explained http://focus.ti.com/lit/an/slva369/slva369.pdf. 

Thanks for your suggestion, however because we have very limited input current we need to use both the -12V and +12V supplies. Therefore, we really need to use the -12V to create the -15V supply and +12V to create the +15V supply. Any help you could provide in creating the -12V to -15V supply would be greatly appretiated.

Attached is a pdf of a buck controller configured as a negative boost converter.  You need a buck controller so that the gate drive polarity is correct.  The active and passive components on the attachment are sized for much higher power than you need but in general this topology will work for you.  If you decided to use this topology, then I suggest sizing the switch, diode, inductor and input and output capacitors using a positive boost converter design guide (e.g. going from 12V to 15V).  The control loop should be similar to that of a boost converter as well.