The STMicroelectronics SM15T24CA is a bidirectional TRANSIL™ TVS diode in the SM15T series, sized for 1500W peak pulse power (10/1000µs waveform). That rating is the budget for absorbing transient energy without failing short. On a nominal 24V DC bus, the 20.5V reverse standoff voltage keeps the diode out of conduction during normal operation, while the 22.8V minimum breakdown voltage ensures the device starts clamping before the rail hits a typical 28V absolute maximum for downstream converters. The 42.8V maximum clamping voltage at the peak pulse current of 234A (8/20µs) defines the upper bound the protected circuitry must survive.
Clamping voltage and the protected circuit's margin
The 42.8V clamp is the number that matters when you size the input capacitors, the DC-DC controller's absolute maximum, and the downstream MOSFET's Vds rating. If the load side can't tolerate 42.8V for the pulse duration, you need a multi-stage clamp or a higher-power device. The 234A peak pulse current (8/20µs) gives the surge current the diode can shunt at that clamp voltage — multiply the two and you get the 1500W peak power rating. On a 24V system, the margin between the 20.5V standoff and the 42.8V clamp is about 22V, which is typical for a single-stage TVS protecting a rail that sees occasional inductive load dumps or lightning-induced surges.
Package and board integration
The SM15T24CA comes in a DO-214AB SMC package, a surface-mount footprint that handles the 1500W pulse without requiring a heatsink — the package's own thermal mass absorbs the short-duration energy. The SMC body is larger than the smaller SMA/SMB packages, which translates to better solder joint reliability under thermal cycling and easier visual inspection. The single bidirectional channel means you place one device across the rail rather than two back-to-back Zeners, saving board area and bill-of-materials line count.
Lifecycle and compliance
The part is RoHS compliant per the TRANSIL™ series environmental compliance.