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Understanding SWIFT Step-Down DC-DC Converters Slide 16

Some performance processors, such as DSPs, FPGAs, and ASICs require sequencing as noted in their datasheets. Implementing power supply sequencing is good design practice as it can help stagger the turn on of multiple power rails to reduce the inrush burden of the upstream power source. Many processor suppliers are good about indicating the sequencing requirements in their datasheets. Sequencing requirements are provided to help designers with problems such as inrush currents and proper start up sequence for the core and I/O of the processor, such as a monotonic start up waveform. Sequencing can be implemented discretely, such as programming the proper soft-start time or using a dedicated power supply sequencer. SWIFT devices with sequencing built in can be chosen as well to reduce component count. A simple scheme for sequencing is performed by using the power good pin of one supply to activate the enable pin of another supply.

PTM Published on: 2011-11-10