Apple Inc.
Interleaved Pulse Frequency Modulation Mode for a Multi-Phase Buck Converter Using Coupled Inductors

Abstract:

A method and apparatus for operating a DC-DC converter in an interleaved (or rotating) pulse frequency modulation (PFM) mode is disclosed. A DC-DC converter includes a number of inductor pairs, with each inductor coupled to a corresponding pulse control circuit. During a cycle in which one of the pulse control circuits sources a current pulse through its respectively coupled inductor, a second pulse control circuit coupled to the other inductor of the pair determines if a voltage on its output node (e.g., where it is coupled to its inductor) is less than a threshold voltage. Responsive to determining that the voltage on its output node is less than the threshold, the second pulse control circuit activates a current path through the other inductor of the pair.