Various diagram

The Dual Output dc-dc Converter Circuit Diagram buck-boost configuration the MAX634 is well suited for dual output dc-dc converters. Only a second winding on the inductor is needed. Typically, this second winding is bifilar-primary and secondary are wound simultaneously using two wires in parallel. 

The inductor core is usually a toroid or a pot core. The negative output voltage is fully regulated by the MAX634. The positive voltage is semi-regulated, and will vary slightly with load changes on either the positive or negative outputs.