A sequencing-sensitive, transient-heavy FPGA power board — worked buck-converter efficiency and thermal calculations, a buck-then-LDO topology strategy, event-based power sequencing, and bulk-plus-ceramic capacitance sizing for a 12A load step.
The project brief: build the power management board for an FPGA/SoC compute system, generating a 5V rail, a 3.3V I/O rail, a 1.8V auxiliary rail, and a 1.2V FPGA core rail — with two requirements that turn a routine four-output board into a real power-design problem. The core rail must reach regulation only after the I/O rail is already stable, a genuine sequencing constraint tied to how the FPGA's I/O protection structures behave during power-up. And the core rail has to survive a 12A load-current step in microseconds when the FPGA fabric wakes a DSP block, without the rail sagging past its allowed voltage budget before the regulator's own control loop can respond.
This module walks the full design the way a real power engineer would: why the high-current core rail uses a synchronous buck while the low-noise analog rail uses an LDO fed from a buck's output, a worked efficiency and junction-temperature calculation for the buck stage, event-based sequencing built on a supervisor IC's power-good monitoring rather than a fixed RC delay, and a bulk-plus-ceramic capacitance bank sized directly from the transient step's numbers. The full worked calculations, complete bill of materials, and finished design reasoning are part of the unlocked module below.