Automotive-grade terminal protection in a dual-package
The UMZ18NFHT106 is a common-anode zener diode array from ROHM Semiconductor, qualified to AEC-Q101 for automotive applications. The 18 V nominal zener voltage clamps transients on signal or low-power supply lines, protecting downstream ICs from overvoltage events. The 200 mW power rating means this is a signal-level protection device — it handles ESD and short-duration surges, not continuous power dissipation. Reverse leakage is specified at 100 nA maximum when biased at 13 V. In a 12 V automotive rail application, that leakage is negligible — it will not pull down a high-impedance sensor output or drain a battery in standby. The common-anode configuration lets you clamp two independent lines to a single reference, saving a package compared to two discrete zeners.
Housed in the SC-70 (SOT-323) surface-mount package, the UMZ18NFHT106 occupies about 2.0 × 2.1 mm of board area. The UMD3 supplier device package is the standard ROHM designation for this footprint. The 150°C maximum junction temperature gives thermal margin in under-hood or engine-bay environments where ambient temperatures can exceed 105°C. The ±2.19% tolerance on the zener voltage is tight enough for clamping thresholds where the exact breakdown point matters — for example, protecting a 15 V rail where you need the zener to conduct before the downstream regulator's abs-max rating.