Why a bidirectional TVS in this package?
The SMAJ26CA-TR is a bidirectional Zener-based transient voltage suppressor from ST's SMAJ TRANSIL™ family. Its single bidirectional channel clamps both positive and negative transients above 26V reverse standoff to 53.5V maximum at the peak pulse current of 43A (8/20µs waveform). No power line protection here — this part is meant for data, I/O, or secondary-side DC bus clamping where you need both polarities covered in one DO-214AC package.
The 53.5V max clamping at 43A (8/20µs) tells you the highest voltage the protected node will see during a surge. If your downstream ICs are rated for, say, 60V absolute maximum, this clamp gives about 6V of margin — tight but workable.
Package and mounting — field-swap reality
The package is a standard surface-mount type, reflow-solderable with typical MSL 1 handling. No exposed pad, no special thermal vias — just a two-pad footprint. For a field-service swap, you'll need a hot-air station or a soldering iron with a fine tip; it's not socketed, so plan for rework if you're replacing it on site. The package marking should include the polarity band for the cathode, but since this is bidirectional, orientation doesn't matter — a nice touch for the repair kit.
STMicroelectronics lists the SMAJ26CA-TR as Active.