Multiple options for generating negative supplies are available. Here are a few example:
- Charge pump based solutions: These generate negative rails usually unregulated for load currents in the 10-100mA. With enough bypass capacitance noise can be well managed.
- A Cuk topology: Typically implemented with a boost regulator a Cuk similar to a SEPIC can generate voltages with an absolute value greater or smaller than the input voltage. SEPIC is used for positive rails and Cuk for negative rails.
Here is a great app note from @ kevintompsett on the subject putting the two topologies to work.
AN-1106: An Improved Topology for Creating Split Rails from a Single Input Voltage
- Inverting buck boost topology (IBB): Typically implemented with a buck regulator the IBB can generate negative voltages as long as the differential voltage between input and output does not exceed the voltage rating of the IC. As an example the ADP2442 36V rated IC can generate -15V from +15V. The ADP2442 is especially good since it can run fully synchronous in this mode.
Here is a great app note from Ricky Yang
AN-1168: Designing an Inverting Power Supply Using the ADP2384/ADP2386 Synchronous Step-Down DC-to-DC Regulators (pdf, 193 kB)
For additional finds remember to use www.analog.com/ADIsimPower
Here is an example of the results: