The buck-boost configurationnf the MAX634 is well suited for dual output de-de 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 semiregulated, and will vary slightly with load changes on either the positive or negative outputs.