A very good Reference Design from TI – Isolated Power Supply for PLC and Data Acquisition: http://www.ti.com/tool/TIDA-00129 Based on a LM5017, a wide Vin Buck Regulator: http://www.ti.com/product/lm5017 Datasheet: http://www.ti.com/lit/gpn/lm5017
MAX15062: PFM from 60v 3v3 or 5V @300mA
MAX15062 : 60V, 300mA, Ultra-Small, High-Efficiency, Synchronous Step-Down, PFM, DC-DC Converter
Product folder: http://www.maximintegrated.com/datasheet/index.mvp/id/7171
EvKits:
3.3 volt MAX15062AEVKIT http://www.maximintegrated.com/datasheet/index.mvp/id/8178
5 volt MAX15062BEVKIT http://www.maximintegrated.com/datasheet/index.mvp/id/8179