28V rail protection — the selection anchor
The reverse standoff voltage of 28V is the maximum continuous DC voltage the device will pass without conducting appreciable leakage — match this to your supply rail or signal line's normal operating voltage. When a surge hits, the clamping voltage is held to 45.4V at the peak pulse current of 13.8A (tested with the standard 10/1000µs waveform).
This is a single-channel bidirectional device, meaning it clamps overvoltage in both positive and negative directions symmetrically. No need to series two unidirectional parts back-to-back — one SMBJ28CA-TR handles it. The breakdown voltage (minimum 31.1V) is the same in both directions, so the protection threshold is identical regardless of polarity.
The DO-214AA (SMB) package is a common surface-mount footprint for TVS diodes in this power class — standard reflow profiles apply, and the package is compatible with automated pick-and-place.