TVS diode for 85.5 V rails — what the ratings mean
The STMicroelectronics SM15T100CA is a bidirectional Zener transient voltage suppressor from the TRANSIL™ series, designed to clamp overvoltage events on a nominal 85.5 V DC rail. Its 1500 W peak pulse power rating (10/1000 µs waveform) means it can absorb a single 56 A surge pulse before the clamping voltage reaches 178 V. This is a protection device, not a regulator — it sits across the rail and stays invisible until the voltage exceeds the 95 V minimum breakdown threshold. The DO-214AB (SMC) surface-mount package handles the thermal transient of a 1500 W pulse without external heatsinking, provided the PCB copper area follows the datasheet's recommended land pattern.
New designs can commit this part without worrying about a sudden discontinuation window. The base part number SM15T100 covers both the bidirectional (CA) and unidirectional (A) variants, all in the same SM15T series.