Input Protection (fuse + TVS)

Three cheap parts between your supply and everything you care about. Each handles a different kind of bad day, and the first two are designed to work as a pair.

• F1 (fuse) — handles too much current: a short somewhere downstream, a failed part. It's the sacrificial element — a 10-cent part that opens so the board survives. Size it ~1.5× your true maximum draw.
• D1 (TVS) — handles too much voltage, on two timescales. Nanosecond spikes (cable transients, ESD, inductive kicks) get clamped at ~26.7 V before anything downstream notices. And a sustained over-voltage — wrong wall adapter — makes the TVS conduct hard, which deliberately blows the fuse. That's the trick: the TVS converts an over-voltage fault into the over-current fault the fuse knows how to handle. Crowbar protection, two parts, no smarts.
• FB1 (ferrite bead) — handles noise: RF riding in on the supply leads becomes a tiny amount of heat in the bead instead of hash on your rail. It's a resistor that only exists at high frequency.

The order matters: fuse first (so the TVS's crowbar current flows through it), clamp second, bead last.

Exposes: vin (5–24 V), vout (same rail, protected, 2 A), gnd.

⚠ A TVS is not a regulator: it does nothing below its 24 V standoff and clamps hard above it. Pick the TVS standoff just above your real supply (24 V TVS for a 24 V rail, SMBJ5.0A for 5 V) — a mismatched one either leaks all day or protects nothing.