1500 W bidirectional TVS for 43.6 V rails
The 1.5SMC51CA-M3/57T: It clamps transients on a 43.6 V nominal rail to 70.1 V maximum, handling 21.4 A of peak pulse current before the junction temperature hits the limit.
What the clamping voltage means for your protection budget
When a surge exceeds the minimum breakdown voltage of 48.5 V, the device avalanches and clamps at 70.1 V maximum across the 21.4 A peak pulse current. The 1500 W rating is derated above 25°C ambient per the datasheet curve; at 125°C the peak pulse power drops to roughly 750 W, so the actual surge-handling margin shrinks in a hot enclosure.
It is a standard catalogue part in the 1.5SMC series, which means ongoing factory support and no forced redesign.
The cathode band is marked for polarity in the unidirectional variant; this bidirectional version has no polarity, so orientation on the PCB is arbitrary. The 1500 W rating assumes a standard copper-land pattern per Vishay's application note; a smaller pad increases thermal resistance and derates the surge capability.