The 1.5SMC120AHM3_A/H is a 1500 W peak-pulse unidirectional TVS diode from Vishay's automotive-grade 1.5SMC TransZorb series, rated for a 102 V reverse standoff and clamping at 165 V with a 9.1 A peak pulse current (10/1000 µs waveform).
Housed in the DO-214AB (SMC) package, the part is surface-mount and mates with a standard SMC footprint — the same pad layout used across the 1.5SMC family. The single unidirectional channel means the cathode band marks the protected side; the anode connects to ground. Peak pulse power of 1500 W at 10/1000 µs is derated above 25 °C per the standard TVS derating curve — at 150 °C junction the effective power drops to about 25 % of the 1500 W rating, so the thermal pad area on the PCB should follow the datasheet's recommended copper land pattern.
Where it lands — automotive and telecom transient protection
Vishay lists this part for Automotive and Telecom applications — think 24 V truck ECUs, 12 V passenger-car body controllers, or 48 V telecom rectifier outputs where a unidirectional clamp shunts positive surges to ground. The TransZorb die structure delivers fast response time typical of silicon-avalanche TVS, clamping within picoseconds of the transient edge.