Voltage thresholds and clamping margin
The SMAJ5.0AQ-13-F: Reverse standoff voltage is 5V, so the diode stays non-conductive under normal 5V supply conditions. Breakdown occurs at 6.4V min, with clamping limited to 9.2V at full peak current — the 4.2V gap between standoff and clamp gives a clean crowbar with margin for a 5V rail. The DO-214AC (SMA) package surface-mounts to standard footprint and supports reflow assembly — no power line protection (the diode is unidirectional, intended for DC rails, not AC mains).