Power Management

Protecting the input, choosing between multiple power sources, and switching rails cleanly — the circuitry that sits between "power in" and your regulators.

Input protection

Threat	Protection
Reverse polarity	Series Schottky (simple) or P-FET (low loss)
Overcurrent	Fuse, PTC resettable fuse, or an eFuse IC
Overvoltage / transients	TVS clamp (see Diodes & Protection)
Inrush	Soft-start / load switch with controlled slew, or NTC

An eFuse IC combines several of these (current limit, OVP, inrush, reverse) in one part — a clean choice for a robust input.

Power path & arbitration (the "arbiter")

When a board can be powered from more than one source — e.g. USB, a DC barrel jack, and a battery — you need to choose which one supplies the load and switch seamlessly between them.

• Diode-OR (ideal-diode OR-ing): each source feeds through an ideal-diode/Schottky; the highest voltage wins. Simple, but no explicit priority.
• Priority muxing / power MUX IC: a power-path / arbiter IC enforces a priority (e.g. "use the wall adapter if present, else battery") and switches make-before-break so the rail never drops.
• PMIC / battery charger with power-path: powers the system and charges the battery from the same input, running from the adapter when present and the battery when not.
• Load switches: gate individual rails on/off (sequencing, standby) with controlled inrush.

Adapter ─┐
USB ─────┤─►  Power-path / arbiter  ─►  System rail  ─►  Regulators
Battery ─┘        (priority + make-before-break)

Sequencing

• If rails must come up in order (core before I/O, etc.), use enable chaining or a supervisor / sequencer, and add power-good signals.

Pick the right level of integration

For anything battery + USB + adapter, reach for a power-path PMIC or arbiter IC rather than discrete diodes — it handles priority, charging and glitch-free switchover for you.

See also

• Power Supplies
• Transistors & MOSFETs — load switches
• Power Topologies