App note: Complex power supply sequencing made easy

Power sequencing from Analog Devices using their ADP5134 sequencer IC. App note here (PDF)

Power supply sequencing is required for microcontrollers, field programmable gate arrays (FPGAs), digital signal processors(DSPs), analog-to-digital converters (ADCs), and other devices that operate from multiple voltage rails. These applications typically require that the core and analog blocks be powered up before the digital input/output (I/O)rails, although some designs may require other sequences. Proper power-up and power-down sequencing can prevent both immediate damage from latch-up and long-term damage from electrostatic discharge (ESD). In addition, sequencing the supplies staggers the inrush current during power-up, an especially helpful technique in applications operating from current-limited supplies.