AEC-Q101 qualification and what it means for the rail
The PTZTFTE254.3B: Nominal zener voltage is 4.55 V with a ±5.49% tolerance — the regulation window spans roughly 4.30 V to 4.80 V, which is tight enough to clamp a 5 V rail without pulling it below the downstream IC's undervoltage lockout threshold.
Power handling and package fit
Rated 1 W continuous power dissipation — at 4.55 V that allows about 220 mA steady-state shunt current before the junction hits the 150 °C limit. The actual derating depends on the PCB copper area under the DO-214AC (SMA) cathode tab; a standard 25 mm² pad keeps the thermal resistance in check. Supplier device package is PMDS — ROHM's internal code for the SMA footprint. The land pattern matches the industry-standard DO-214AC solder pad, so no footprint adjustment is needed when swapping between ROHM and other SMA zener sources.
ROHS3 compliant — no restricted substances above the threshold limits, no exemption expiry clock to track for EU or UKCA market entry.