Must be high enough to limit ripple current, but low enough to allow fast transient response.
A Java-based tool to calculate voltages, currents, and Bode plots for over 20 topologies. TI Power Supply Design Seminars
The demand for Fundamentals of Power Supply Design in PDF format stems from its utility:
Can either step up or step down the voltage, reversing the output polarity in its classic form. Isolated Topologies